diff --git a/frontend/src/lib/components/Button.svelte b/frontend/src/lib/components/Button.svelte
new file mode 100644
index 00000000..c2968a2d
--- /dev/null
+++ b/frontend/src/lib/components/Button.svelte
@@ -0,0 +1,43 @@
+<script lang="ts">
+	import type { Snippet } from 'svelte';
+	import Icon from '$lib/icons/Icon.svelte';
+
+	type Variant = 'primary' | 'secondary' | 'danger';
+
+	interface Props {
+		/** Visual style → `.btn-{variant}` (default `secondary`). */
+		variant?: Variant;
+		/** Optional leading icon-registry name. */
+		icon?: string;
+		/** Compact size → adds `.btn-sm`. */
+		small?: boolean;
+		type?: 'button' | 'submit' | 'reset';
+		disabled?: boolean;
+		title?: string;
+		onclick?: (e: MouseEvent) => void;
+		/** Extra classes appended after the base `.btn` classes. */
+		class?: string;
+		children?: Snippet;
+	}
+
+	let {
+		variant = 'secondary',
+		icon,
+		small = false,
+		type = 'button',
+		disabled = false,
+		title,
+		onclick,
+		class: cls = '',
+		children
+	}: Props = $props();
+
+	const className = $derived(
+		['btn', `btn-${variant}`, small ? 'btn-sm' : '', cls].filter(Boolean).join(' ')
+	);
+</script>
+
+<button class={className} {type} {disabled} {title} {onclick}>
+	{#if icon}<Icon name={icon} />{/if}
+	{@render children?.()}
+</button>
diff --git a/frontend/src/lib/components/EmptyState.svelte b/frontend/src/lib/components/EmptyState.svelte
new file mode 100644
index 00000000..4403103f
--- /dev/null
+++ b/frontend/src/lib/components/EmptyState.svelte
@@ -0,0 +1,54 @@
+<script lang="ts">
+	import type { Snippet } from 'svelte';
+	import Icon from '$lib/icons/Icon.svelte';
+
+	interface Props {
+		/** Icon-registry name shown above the title (omit for a text-only state). */
+		icon?: string;
+		/** Primary line. */
+		title?: string;
+		/** Secondary explanatory line. */
+		hint?: string;
+		/** Error styling (danger-coloured icon) + assertive `role="alert"`. */
+		error?: boolean;
+		/** Extra content (e.g. a call-to-action button) rendered below the hint. */
+		children?: Snippet;
+	}
+
+	let { icon, title, hint, error = false, children }: Props = $props();
+</script>
+
+<div class="empty-state" class:empty-state--error={error} role={error ? 'alert' : undefined}>
+	{#if icon}<Icon name={icon} class="empty-state__icon" />{/if}
+	{#if title}<p class="empty-state__title">{title}</p>{/if}
+	{#if hint}<p class="empty-state__hint">{hint}</p>{/if}
+	{@render children?.()}
+</div>
+
+<style>
+	/* Layout comes from the global `.empty-state` (styles/ported/content.css);
+	   these refine the icon/title/hint elements consistently across views. */
+	.empty-state :global(.empty-state__icon) {
+		font-size: var(--text-5xl);
+		color: var(--color-text-faint);
+		margin-bottom: var(--space-2);
+	}
+
+	.empty-state--error :global(.empty-state__icon) {
+		color: var(--color-danger-text);
+	}
+
+	.empty-state__title {
+		margin: 0;
+		font-size: var(--text-lg);
+		font-weight: var(--weight-semibold);
+		color: var(--color-text-heading);
+	}
+
+	.empty-state__hint {
+		margin: 0;
+		max-width: 28rem;
+		font-size: var(--text-sm);
+		color: var(--color-text-muted);
+	}
+</style>
diff --git a/frontend/src/lib/components/MoveDialog.svelte b/frontend/src/lib/components/MoveDialog.svelte
index 41579cd0..42436d75 100644
--- a/frontend/src/lib/components/MoveDialog.svelte
+++ b/frontend/src/lib/components/MoveDialog.svelte
@@ -1,4 +1,5 @@
 <script lang="ts">
+	import { errorToast } from '$lib/utils/errors';
 	import { listFolder, moveFolder } from '$lib/api/endpoints/folders';
 	import { moveFile } from '$lib/api/endpoints/files';
 	import { copyFiles, copyFolders } from '$lib/api/endpoints/batch';
@@ -42,7 +43,7 @@
 			currentId = id;
 			folders = (await listFolder(id)).folders;
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		} finally {
 			loading = false;
 		}
@@ -98,7 +99,7 @@
 			open = false;
 			onmoved?.();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		} finally {
 			working = false;
 		}
diff --git a/frontend/src/lib/components/ResourceList.svelte b/frontend/src/lib/components/ResourceList.svelte
index 4f4b4da3..742fcb86 100644
--- a/frontend/src/lib/components/ResourceList.svelte
+++ b/frontend/src/lib/components/ResourceList.svelte
@@ -51,6 +51,8 @@
 <script lang="ts">
 	import type { Snippet } from 'svelte';
 	import Icon from '$lib/icons/Icon.svelte';
+	import EmptyState from '$lib/components/EmptyState.svelte';
+	import SkeletonList from '$lib/components/SkeletonList.svelte';
 	import ListToolbar from '$lib/components/ListToolbar.svelte';
 	import { t } from '$lib/i18n/index.svelte';
 	import { files as filesStore } from '$lib/stores/files.svelte';
@@ -396,37 +398,15 @@
 {/if}
 
 {#if error}
-	<div class="empty-state">
-		<Icon name="exclamation-circle" class="empty-state-icon empty-state-icon--error" />
-		<p>{error}</p>
-	</div>
+	<EmptyState icon="exclamation-circle" title={error} error />
 {:else if loading && isEmpty}
-	<div class="files-container">
-		<div
-			class={filesStore.viewMode === 'grid' ? 'files-grid-view files-skeleton' : 'files-skeleton'}
-		>
-			{#each SKELETON as i (i)}
-				{#if filesStore.viewMode === 'grid'}
-					<div class="skeleton-card">
-						<div class="skeleton skeleton-thumb"></div>
-						<div class="skeleton skeleton-line skeleton-line--medium"></div>
-					</div>
-				{:else}
-					<div class="skeleton-row">
-						<div class="skeleton skeleton-icon"></div>
-						<div class="skeleton skeleton-line skeleton-line--medium"></div>
-						<div class="skeleton skeleton-line skeleton-line--short"></div>
-					</div>
-				{/if}
-			{/each}
-		</div>
-	</div>
+	<SkeletonList count={SKELETON.length} />
 {:else if isEmpty}
-	<div class="empty-state">
-		{#if emptyIcon}<Icon name={emptyIcon} class="empty-state-icon" />{/if}
-		<p>{emptyText ?? t('common.empty', 'Nothing here yet.')}</p>
-		{#if emptyHint}<p class="empty-state__hint">{emptyHint}</p>{/if}
-	</div>
+	<EmptyState
+		icon={emptyIcon}
+		title={emptyText ?? t('common.empty', 'Nothing here yet.')}
+		hint={emptyHint}
+	/>
 {:else}
 	<div class="files-container">
 		<div class={viewClass} style="--files-list-columns: {columns}">
@@ -690,20 +670,4 @@
 	.rl-ctx-item--danger {
 		color: var(--color-danger-text);
 	}
-
-	.empty-state__hint {
-		color: var(--color-text-muted);
-		font-size: var(--text-sm);
-	}
-
-	/* Empty/error icon lives inside the <Icon> child component's <svg>. */
-	.empty-state :global(.empty-state-icon) {
-		font-size: var(--text-5xl);
-		color: var(--color-text-faint);
-		margin-bottom: var(--space-2);
-	}
-
-	.empty-state :global(.empty-state-icon--error) {
-		color: var(--color-danger-text);
-	}
 </style>
diff --git a/frontend/src/lib/components/ShareDialog.svelte b/frontend/src/lib/components/ShareDialog.svelte
index e3602d21..a0413d00 100644
--- a/frontend/src/lib/components/ShareDialog.svelte
+++ b/frontend/src/lib/components/ShareDialog.svelte
@@ -1,4 +1,5 @@
 <script lang="ts">
+	import { errorToast } from '$lib/utils/errors';
 	import {
 		copyShareLink,
 		createShare,
@@ -118,7 +119,7 @@
 			directoryAvailable = isDirectoryAvailable();
 			members = groupGrants(await fetchGrantsForResource(item.kind, item.id));
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		} finally {
 			grantsLoading = false;
 		}
@@ -153,7 +154,7 @@
 			summarizeNotifications(res.notification.outcomes);
 			await loadGrants();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -168,7 +169,7 @@
 			);
 			await loadGrants();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -183,7 +184,7 @@
 			);
 			await loadGrants();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -192,7 +193,7 @@
 			for (const id of m.grantIds) await revokeGrant(id);
 			await loadGrants();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -202,7 +203,7 @@
 			const set = await notifyGrantRecipient(m.notifyGrantId);
 			summarizeNotifications(set.outcomes);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -252,7 +253,7 @@
 		try {
 			shares = await listSharesForItem(item.id, item.kind);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		} finally {
 			linkLoading = false;
 		}
@@ -275,7 +276,7 @@
 			await loadShares();
 			ui.notify(t('share.created', 'Public link created'), 'success');
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		} finally {
 			creating = false;
 		}
@@ -286,7 +287,7 @@
 			await updateShare(share.id, { expiresAt: expiry });
 			await loadShares();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -301,7 +302,7 @@
 				'success'
 			);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -310,7 +311,7 @@
 			await deleteShare(share.id);
 			shares = shares.filter((s) => s.id !== share.id);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
diff --git a/frontend/src/lib/components/SkeletonList.svelte b/frontend/src/lib/components/SkeletonList.svelte
new file mode 100644
index 00000000..6eea2cb9
--- /dev/null
+++ b/frontend/src/lib/components/SkeletonList.svelte
@@ -0,0 +1,32 @@
+<script lang="ts">
+	import { files as filesStore } from '$lib/stores/files.svelte';
+
+	interface Props {
+		/** Number of placeholder cards/rows to render (default 6). */
+		count?: number;
+	}
+
+	let { count = 6 }: Props = $props();
+
+	const placeholders = $derived(Array.from({ length: count }, (_, i) => i));
+</script>
+
+<div class="files-container">
+	<div class={filesStore.viewMode === 'grid' ? 'files-grid-view files-skeleton' : 'files-skeleton'}>
+		{#each placeholders as i (i)}
+			{#if filesStore.viewMode === 'grid'}
+				<div class="skeleton-card">
+					<div class="skeleton skeleton-thumb"></div>
+					<div class="skeleton skeleton-line skeleton-line--medium"></div>
+					<div class="skeleton skeleton-line skeleton-line--short"></div>
+				</div>
+			{:else}
+				<div class="skeleton-row">
+					<div class="skeleton skeleton-icon"></div>
+					<div class="skeleton skeleton-line skeleton-line--medium"></div>
+					<div class="skeleton skeleton-line skeleton-line--short"></div>
+				</div>
+			{/if}
+		{/each}
+	</div>
+</div>
diff --git a/frontend/src/lib/components/WopiEditor.svelte b/frontend/src/lib/components/WopiEditor.svelte
index f60338e4..8c2cfc7c 100644
--- a/frontend/src/lib/components/WopiEditor.svelte
+++ b/frontend/src/lib/components/WopiEditor.svelte
@@ -1,8 +1,8 @@
 <script lang="ts">
+	import { errorToast } from '$lib/utils/errors';
 	import { getEditorUrlWithFallback } from '$lib/api/endpoints/wopi';
 	import Icon from '$lib/icons/Icon.svelte';
 	import { t } from '$lib/i18n/index.svelte';
-	import { ui } from '$lib/stores/ui.svelte';
 
 	interface Props {
 		open: boolean;
@@ -68,7 +68,7 @@
 				queueMicrotask(() => form?.submit());
 			})
 			.catch((e) => {
-				ui.notify(e instanceof Error ? e.message : String(e), 'error');
+				errorToast(e);
 				close();
 			})
 			.finally(() => (loading = false));
diff --git a/frontend/src/lib/composables/useOwnerCache.svelte.ts b/frontend/src/lib/composables/useOwnerCache.svelte.ts
new file mode 100644
index 00000000..f66fe4bb
--- /dev/null
+++ b/frontend/src/lib/composables/useOwnerCache.svelte.ts
@@ -0,0 +1,48 @@
+/**
+ * Reactive cache of owner-id → display-name, with memoised parallel resolution.
+ *
+ * Replaces the identical `ownerNames` record + `resolveOwners()` block in the
+ * favorites and recent views. The id→name resolver is injected so the cache
+ * stays decoupled from any specific API endpoint.
+ */
+export class OwnerCache {
+	#names = $state<Record<string, string>>({});
+	#resolver: (id: string) => Promise<string>;
+
+	constructor(resolver: (id: string) => Promise<string>) {
+		this.#resolver = resolver;
+	}
+
+	/** Resolved names so far (id → display name). */
+	get names(): Record<string, string> {
+		return this.#names;
+	}
+
+	/** Display name for an id, or `null` when unknown/empty (for cell rendering). */
+	name(id: string | null | undefined): string | null {
+		if (!id) return null;
+		return this.#names[id] ?? null;
+	}
+
+	/** Display name for an id, falling back to the id itself (for group labels). */
+	label(id: string): string {
+		return this.#names[id] ?? id;
+	}
+
+	/** Resolve every not-yet-cached id in parallel; nullish ids are skipped. */
+	async resolve(ids: Iterable<string | null | undefined>): Promise<void> {
+		const unique = [...new Set([...ids].filter((id): id is string => !!id))];
+		await Promise.all(
+			unique.map(async (id) => {
+				if (this.#names[id]) return;
+				const name = await this.#resolver(id);
+				this.#names = { ...this.#names, [id]: name };
+			})
+		);
+	}
+}
+
+/** Create a reactive {@link OwnerCache} backed by `resolver`. */
+export function useOwnerCache(resolver: (id: string) => Promise<string>): OwnerCache {
+	return new OwnerCache(resolver);
+}
diff --git a/frontend/src/lib/composables/useSelection.svelte.ts b/frontend/src/lib/composables/useSelection.svelte.ts
new file mode 100644
index 00000000..beadc2ef
--- /dev/null
+++ b/frontend/src/lib/composables/useSelection.svelte.ts
@@ -0,0 +1,65 @@
+/**
+ * Reactive multi-select over string ids. Backs the repeated
+ * `let selected = $state(new Set()); function toggle(id) { … }` pattern used by
+ * the photos grid, music picker and other list views with one source of truth.
+ *
+ * Mutations swap in a fresh Set so `$derived`/template reads re-run.
+ */
+export class Selection {
+	#ids = $state<Set<string>>(new Set());
+
+	/** The live selection set (read-only intent — mutate via the methods). */
+	get ids(): Set<string> {
+		return this.#ids;
+	}
+
+	get size(): number {
+		return this.#ids.size;
+	}
+
+	get isEmpty(): boolean {
+		return this.#ids.size === 0;
+	}
+
+	has(id: string): boolean {
+		return this.#ids.has(id);
+	}
+
+	/** Selected ids as an array (e.g. for batch API calls). */
+	values(): string[] {
+		return [...this.#ids];
+	}
+
+	toggle(id: string): void {
+		const next = new Set(this.#ids);
+		if (next.has(id)) next.delete(id);
+		else next.add(id);
+		this.#ids = next;
+	}
+
+	add(id: string): void {
+		if (this.#ids.has(id)) return;
+		this.#ids = new Set(this.#ids).add(id);
+	}
+
+	delete(id: string): void {
+		if (!this.#ids.has(id)) return;
+		const next = new Set(this.#ids);
+		next.delete(id);
+		this.#ids = next;
+	}
+
+	/** Replace the whole selection. */
+	set(ids: Iterable<string>): void {
+		this.#ids = new Set(ids);
+	}
+
+	clear(): void {
+		if (this.#ids.size) this.#ids = new Set();
+	}
+}
+
+/** Create a reactive {@link Selection}. */
+export function useSelection(): Selection {
+	return new Selection();
+}
diff --git a/frontend/src/lib/stores/dialogs.svelte.ts b/frontend/src/lib/stores/dialogs.svelte.ts
index 452f7aa8..2b44c981 100644
--- a/frontend/src/lib/stores/dialogs.svelte.ts
+++ b/frontend/src/lib/stores/dialogs.svelte.ts
@@ -7,6 +7,8 @@
  * and only closes the dialog if it resolves. A rejection keeps the dialog open
  * and surfaces an inline error, so failed renames/deletes don't silently vanish.
  */
+import { errorMessage } from '$lib/utils/errors';
+
 export interface ConfirmOptions {
 	title: string;
 	message?: string;
@@ -87,7 +89,7 @@ class DialogStore {
 				else await (action as (v: string) => Promise<void> | void)(value as string);
 			} catch (err) {
 				this.busy = false;
-				this.error = err instanceof Error ? err.message : String(err);
+				this.error = errorMessage(err);
 				return; // keep the dialog open
 			}
 		}
diff --git a/frontend/src/lib/stores/files.svelte.ts b/frontend/src/lib/stores/files.svelte.ts
index 1883ded4..afd5200c 100644
--- a/frontend/src/lib/stores/files.svelte.ts
+++ b/frontend/src/lib/stores/files.svelte.ts
@@ -7,6 +7,10 @@
 import type { FolderItem } from '$lib/api/types';
 import { t } from '$lib/i18n/index.svelte';
 
+// Re-exported so the files view's grouping-helper barrel stays a single import
+// site; the implementation lives in the shared time util.
+export { relativeTimeAgo } from '$lib/utils/time';
+
 export type ViewMode = 'grid' | 'list';
 
 // ── Group-by / display helpers ───────────────────────────────────────────────
@@ -41,28 +45,6 @@ export function dateBucket(value: number | null | undefined): string {
 	return String(toDate(value).getFullYear());
 }
 
-/** Locale-aware relative "time ago" for grid-card metadata lines. */
-export function relativeTimeAgo(value: number | null | undefined): string {
-	if (!value) return '';
-	const date = toDate(value);
-	if (Number.isNaN(date.getTime())) return '';
-	const diffSec = Math.round((date.getTime() - Date.now()) / 1000);
-	const abs = Math.abs(diffSec);
-	const rtf = new Intl.RelativeTimeFormat(undefined, { numeric: 'auto' });
-	const units: Array<[Intl.RelativeTimeFormatUnit, number]> = [
-		['year', 31536000],
-		['month', 2592000],
-		['week', 604800],
-		['day', 86400],
-		['hour', 3600],
-		['minute', 60]
-	];
-	for (const [unit, secs] of units) {
-		if (abs >= secs) return rtf.format(Math.round(diffSec / secs), unit);
-	}
-	return rtf.format(diffSec, 'second');
-}
-
 /** Localise a file `category` (e.g. "Image") via files.file_types.* keys. */
 export function typeLabel(category: string | null | undefined): string {
 	if (!category) return t('files.file_types.document', 'Document');
diff --git a/frontend/src/lib/utils/errors.ts b/frontend/src/lib/utils/errors.ts
new file mode 100644
index 00000000..4b4ddfd6
--- /dev/null
+++ b/frontend/src/lib/utils/errors.ts
@@ -0,0 +1,15 @@
+/** Error-handling helpers shared across pages and components. */
+import { ui } from '$lib/stores/ui.svelte';
+
+/** Normalise an unknown thrown value into a human-readable message. */
+export function errorMessage(e: unknown): string {
+	return e instanceof Error ? e.message : String(e);
+}
+
+/**
+ * Raise an error toast for a caught value — the canonical catch-block handler.
+ * Replaces the repeated `ui.notify(e instanceof Error ? e.message : String(e), 'error')`.
+ */
+export function errorToast(e: unknown): void {
+	ui.notify(errorMessage(e), 'error');
+}
diff --git a/frontend/src/lib/utils/time.ts b/frontend/src/lib/utils/time.ts
new file mode 100644
index 00000000..b5f52f04
--- /dev/null
+++ b/frontend/src/lib/utils/time.ts
@@ -0,0 +1,43 @@
+/** Time-formatting helpers shared across views. */
+
+/** Options for {@link relativeTimeAgo}. */
+export interface RelativeTimeOptions {
+	/** Label returned for a null/empty value (default `''`). */
+	empty?: string;
+	/** When the value can't be parsed, return it stringified instead of `empty`. */
+	invalidAsString?: boolean;
+}
+
+/**
+ * Locale-aware relative "time ago" via `Intl.RelativeTimeFormat`.
+ *
+ * Accepts an epoch (seconds or milliseconds) or an ISO-8601 string, so the
+ * grid-card metadata lines (epoch) and the profile/app-password tables (ISO)
+ * share one implementation.
+ */
+export function relativeTimeAgo(
+	value: number | string | null | undefined,
+	opts: RelativeTimeOptions = {}
+): string {
+	const empty = opts.empty ?? '';
+	if (value === null || value === undefined || value === '') return empty;
+	const date =
+		typeof value === 'number' ? new Date(value < 1e12 ? value * 1000 : value) : new Date(value);
+	if (Number.isNaN(date.getTime())) return opts.invalidAsString ? String(value) : empty;
+
+	const diffSec = Math.round((date.getTime() - Date.now()) / 1000);
+	const abs = Math.abs(diffSec);
+	const rtf = new Intl.RelativeTimeFormat(undefined, { numeric: 'auto' });
+	const units: Array<[Intl.RelativeTimeFormatUnit, number]> = [
+		['year', 31536000],
+		['month', 2592000],
+		['week', 604800],
+		['day', 86400],
+		['hour', 3600],
+		['minute', 60]
+	];
+	for (const [unit, secs] of units) {
+		if (abs >= secs) return rtf.format(Math.round(diffSec / secs), unit);
+	}
+	return rtf.format(diffSec, 'second');
+}
diff --git a/frontend/src/routes/admin/+page.svelte b/frontend/src/routes/admin/+page.svelte
index 164a06a7..153fa157 100644
--- a/frontend/src/routes/admin/+page.svelte
+++ b/frontend/src/routes/admin/+page.svelte
@@ -1,4 +1,5 @@
 <script lang="ts">
+	import { errorMessage, errorToast } from '$lib/utils/errors';
 	import {
 		clearPluginLogs,
 		createUser,
@@ -112,7 +113,7 @@
 		try {
 			dashboard = await getDashboard();
 		} catch (e) {
-			dashboardError = e instanceof Error ? e.message : String(e);
+			dashboardError = errorMessage(e);
 		}
 	}
 
@@ -141,7 +142,7 @@
 		try {
 			smtpResult = await sendSmtpTest(smtpTo.trim());
 		} catch (e) {
-			smtpResult = { success: false, message: e instanceof Error ? e.message : String(e) };
+			smtpResult = { success: false, message: errorMessage(e) };
 		} finally {
 			smtpSending = false;
 		}
@@ -157,7 +158,7 @@
 		try {
 			oidc = await getOidcSettings();
 		} catch (e) {
-			oidcMsg = { text: e instanceof Error ? e.message : String(e), ok: false };
+			oidcMsg = { text: errorMessage(e), ok: false };
 		}
 	}
 	async function runOidcTest() {
@@ -185,7 +186,7 @@
 			});
 			oidcMsg = { text: t('admin.settings_saved_ok', 'Settings saved.'), ok: true };
 		} catch (e) {
-			oidcMsg = { text: e instanceof Error ? e.message : String(e), ok: false };
+			oidcMsg = { text: errorMessage(e), ok: false };
 		} finally {
 			oidcSaving = false;
 		}
@@ -246,7 +247,7 @@
 				pathStyle: storage.s3_force_path_style ?? false
 			};
 		} catch (e) {
-			storageMsg = { text: e instanceof Error ? e.message : String(e), ok: false };
+			storageMsg = { text: errorMessage(e), ok: false };
 		}
 	}
 	function applyPreset() {
@@ -275,7 +276,7 @@
 			storageMsg = { text: t('admin.storage_saved', 'Storage settings saved.'), ok: true };
 			await loadStorage();
 		} catch (e) {
-			storageMsg = { text: e instanceof Error ? e.message : String(e), ok: false };
+			storageMsg = { text: errorMessage(e), ok: false };
 		} finally {
 			storageBusy = false;
 		}
@@ -299,7 +300,7 @@
 				};
 			}
 		} catch (e) {
-			storageMsg = { text: e instanceof Error ? e.message : String(e), ok: false };
+			storageMsg = { text: errorMessage(e), ok: false };
 		} finally {
 			storageBusy = false;
 		}
@@ -347,7 +348,7 @@
 		try {
 			verifyResult = await verifyMigration(100);
 		} catch (e) {
-			verifyError = e instanceof Error ? e.message : String(e);
+			verifyError = errorMessage(e);
 		} finally {
 			verifying = false;
 		}
@@ -505,7 +506,7 @@
 			});
 			retentionMsg = t('admin.plugins_retention_saved', 'Retention saved.');
 		} catch (e) {
-			retentionMsg = e instanceof Error ? e.message : String(e);
+			retentionMsg = errorMessage(e);
 		}
 	}
 	async function purgeLogs() {
@@ -541,7 +542,7 @@
 			};
 			await loadPlugins();
 		} catch (err) {
-			installMsg = { ok: false, text: err instanceof Error ? err.message : String(err) };
+			installMsg = { ok: false, text: errorMessage(err) };
 		} finally {
 			installing = false;
 			input.value = '';
@@ -609,7 +610,7 @@
 			users = page.users;
 			total = page.total;
 		} catch (e) {
-			usersError = e instanceof Error ? e.message : String(e);
+			usersError = errorMessage(e);
 		}
 	}
 
@@ -620,12 +621,12 @@
 			pluginsAvailable = res.available;
 			plugins = res.plugins;
 		} catch (e) {
-			pluginsError = e instanceof Error ? e.message : String(e);
+			pluginsError = errorMessage(e);
 		}
 	}
 
 	function reportError(e: unknown) {
-		ui.notify(e instanceof Error ? e.message : String(e), 'error');
+		errorToast(e);
 	}
 
 	async function copyText(text: string) {
@@ -720,7 +721,7 @@
 			resetModal = null;
 			ui.notify(t('admin.password_reset', 'Password reset'), 'success');
 		} catch (err) {
-			resetError = err instanceof Error ? err.message : String(err);
+			resetError = errorMessage(err);
 		} finally {
 			resetting = false;
 		}
@@ -776,7 +777,7 @@
 			};
 			await loadUsers();
 		} catch (err) {
-			createError = err instanceof Error ? err.message : String(err);
+			createError = errorMessage(err);
 		} finally {
 			creating = false;
 		}
diff --git a/frontend/src/routes/device/+page.svelte b/frontend/src/routes/device/+page.svelte
index 018f2e03..a82a4239 100644
--- a/frontend/src/routes/device/+page.svelte
+++ b/frontend/src/routes/device/+page.svelte
@@ -1,4 +1,5 @@
 <script lang="ts">
+	import { errorMessage } from '$lib/utils/errors';
 	import { page } from '$app/state';
 	import { onMount } from 'svelte';
 	import {
@@ -37,7 +38,7 @@
 					return t('device.lookup_failed', 'Failed to verify code. Please try again.');
 			}
 		}
-		return err instanceof Error ? err.message : String(err);
+		return errorMessage(err);
 	}
 
 	async function lookup(e?: SubmitEvent) {
@@ -83,7 +84,7 @@
 			await decideDevice(code, action);
 			step = action === 'approve' ? 'approved' : 'denied';
 		} catch (err) {
-			errorText = err instanceof Error ? err.message : String(err);
+			errorText = errorMessage(err);
 			step = 'error';
 		} finally {
 			busy = false;
diff --git a/frontend/src/routes/favorites/+page.svelte b/frontend/src/routes/favorites/+page.svelte
index 4851810f..c5d7965c 100644
--- a/frontend/src/routes/favorites/+page.svelte
+++ b/frontend/src/routes/favorites/+page.svelte
@@ -1,4 +1,7 @@
 <script lang="ts">
+	import Button from '$lib/components/Button.svelte';
+	import { useOwnerCache } from '$lib/composables/useOwnerCache.svelte';
+	import { errorToast } from '$lib/utils/errors';
 	import { goto } from '$app/navigation';
 	import { onMount } from 'svelte';
 	import {
@@ -14,7 +17,6 @@
 	import { renameFile, deleteFile } from '$lib/api/endpoints/files';
 	import { renameFolder, deleteFolder } from '$lib/api/endpoints/folders';
 	import type { FileItem } from '$lib/api/types';
-	import Icon from '$lib/icons/Icon.svelte';
 	import FileViewer from '$lib/components/FileViewer.svelte';
 	import MoveDialog from '$lib/components/MoveDialog.svelte';
 	import ShareDialog from '$lib/components/ShareDialog.svelte';
@@ -25,7 +27,6 @@
 	} from '$lib/components/ResourceList.svelte';
 	import { confirmDialog, promptDialog } from '$lib/stores/dialogs.svelte';
 	import { t } from '$lib/i18n/index.svelte';
-	import { ui } from '$lib/stores/ui.svelte';
 
 	let raw = $state<FavoritesResourceItem[]>([]);
 	let cursor = $state<string | undefined>(undefined);
@@ -33,7 +34,7 @@
 	let error = $state<string | null>(null);
 	let groupBy = $state('');
 	let reversed = $state(false);
-	let ownerNames = $state<Record<string, string>>({});
+	const owners = useOwnerCache(resolveOwnerName);
 
 	const byId = $derived(new Map(raw.map((it) => [it.resource.id, it])));
 
@@ -50,7 +51,7 @@
 				size: isFile ? (it.resource as FileItem).size : null,
 				date: it.favorited_at,
 				ownerId,
-				ownerName: ownerId ? (ownerNames[ownerId] ?? null) : null,
+				ownerName: owners.name(ownerId),
 				isFavorite: true,
 				category: isFile ? it.resource.category : 'Folder',
 				modifiedAt: it.resource.modified_at
@@ -65,7 +66,7 @@
 			label: t('groupby.owner', 'Owner'),
 			orderBy: 'owner',
 			bucketOf: (e) => e.ownerId ?? null,
-			labelOf: (id) => ownerNames[id] ?? id
+			labelOf: (id) => owners.label(id)
 		},
 		{
 			key: 'type',
@@ -94,19 +95,6 @@
 		}
 	];
 
-	async function resolveOwners(items: FavoritesResourceItem[]) {
-		const ids = [
-			...new Set(items.map((i) => i.resource.owner_id).filter((id): id is string => !!id))
-		];
-		await Promise.all(
-			ids.map(async (id) => {
-				if (ownerNames[id]) return;
-				const name = await resolveOwnerName(id);
-				ownerNames = { ...ownerNames, [id]: name };
-			})
-		);
-	}
-
 	async function load(reset = false, orderBy = 'name', rev = reversed) {
 		loading = true;
 		error = null;
@@ -119,7 +107,7 @@
 			});
 			raw = reset ? page.items : [...raw, ...page.items];
 			cursor = page.next_cursor;
-			void resolveOwners(page.items);
+			void owners.resolve(page.items.map((i) => i.resource.owner_id));
 		} catch (e) {
 			console.error('favorites: load error', e);
 			error = t('errors_loadFailed', 'Failed to load items');
@@ -152,7 +140,7 @@
 			await removeFavorite(entry.kind, entry.id);
 			raw = raw.filter((i) => i.resource.id !== entry.id);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -175,7 +163,7 @@
 			else await renameFolder(entry.id, name);
 			await load(true, orderByForGroup());
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -192,7 +180,7 @@
 			else await deleteFolder(entry.id);
 			raw = raw.filter((i) => i.resource.id !== entry.id);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -268,7 +256,7 @@
 			raw = raw.filter((i) => !removed.has(i.resource.id));
 			selectedIds = new Set();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -302,22 +290,18 @@
 	onselectionchange={(ids) => (selectedIds = ids)}
 >
 	{#snippet batchToolbar()}
-		<button class="btn btn-secondary" onclick={batchDownload}>
-			<Icon name="download" />
-			{t('common.download', 'Download')}
-		</button>
-		<button
-			class="btn btn-secondary"
+		<Button icon="download" onclick={batchDownload}>{t('common.download', 'Download')}</Button>
+		<Button
+			icon="arrows-alt"
 			onclick={() => {
 				moveTarget = null;
 				moveItems = batchTargets();
 				moveOpen = true;
-			}}><Icon name="arrows-alt" /> {t('files.move', 'Move')}</button
+			}}>{t('files.move', 'Move')}</Button
+		>
+		<Button variant="danger" icon="trash" onclick={batchDelete}
+			>{t('common.delete', 'Delete')}</Button
 		>
-		<button class="btn btn-danger" onclick={batchDelete}>
-			<Icon name="trash" />
-			{t('common.delete', 'Delete')}
-		</button>
 	{/snippet}
 </ResourceList>
 
diff --git a/frontend/src/routes/files/[...path]/+page.svelte b/frontend/src/routes/files/[...path]/+page.svelte
index 8421f538..5422b912 100644
--- a/frontend/src/routes/files/[...path]/+page.svelte
+++ b/frontend/src/routes/files/[...path]/+page.svelte
@@ -1,4 +1,7 @@
 <script lang="ts">
+	import SkeletonList from '$lib/components/SkeletonList.svelte';
+	import EmptyState from '$lib/components/EmptyState.svelte';
+	import { errorMessage, errorToast } from '$lib/utils/errors';
 	import { goto } from '$app/navigation';
 	import { page } from '$app/state';
 	import Icon from '$lib/icons/Icon.svelte';
@@ -121,7 +124,7 @@
 			if (isFav) await removeFavorite(kind, id);
 			else await addFavorite(kind, id);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 			await loadBadges();
 		}
 	}
@@ -213,7 +216,7 @@
 			await createFolder(name, currentId);
 			await load();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -259,7 +262,7 @@
 			ui.finishProgress(nid, done, 'success');
 			await load();
 		} catch (err) {
-			ui.finishProgress(nid, err instanceof Error ? err.message : String(err), 'error');
+			ui.finishProgress(nid, errorMessage(err), 'error');
 		} finally {
 			uploading = false;
 		}
@@ -292,7 +295,7 @@
 			else await renameFolder(id, name);
 			await load();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -309,7 +312,7 @@
 			else await deleteFolder(id);
 			await load();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -433,7 +436,7 @@
 			a.remove();
 			URL.revokeObjectURL(url);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -460,7 +463,7 @@
 			clearSelection();
 			void loadBadges();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -523,7 +526,7 @@
 				if (folder) await deleteFolder(id);
 				else await deleteFile(id);
 			} catch (e) {
-				ui.notify(e instanceof Error ? e.message : String(e), 'error');
+				errorToast(e);
 			}
 		}
 		clearSelection();
@@ -568,7 +571,7 @@
 			clearSelection();
 			await load();
 		} catch (err) {
-			ui.notify(err instanceof Error ? err.message : String(err), 'error');
+			errorToast(err);
 		}
 	}
 
@@ -644,7 +647,7 @@
 			else window.open(url, '_blank');
 		} catch (e) {
 			win?.close();
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -663,7 +666,7 @@
 		try {
 			playlists = await listPlaylists();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 			return;
 		}
 		const existing = playlists.map((p) => p.name).join(', ');
@@ -686,7 +689,7 @@
 			await addTracks(playlist.id, [file.id]);
 			ui.notify(t('music.added_to_playlist', 'Added to playlist'), 'success');
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -745,7 +748,7 @@
 			ui.notify(t('files.uploaded', 'Upload complete'), 'success');
 			await load();
 		} catch (err) {
-			ui.notify(err instanceof Error ? err.message : String(err), 'error');
+			errorToast(err);
 		} finally {
 			uploading = false;
 			input.value = '';
@@ -1076,36 +1079,14 @@
 	</div>
 
 	{#if error}
-		<div class="empty-state"><p>{error}</p></div>
+		<EmptyState title={error} error />
 	{:else if showSkeleton && isEmpty}
-		<div class="files-container">
-			<div
-				class={viewClass === 'files-grid-view'
-					? 'files-grid-view files-skeleton'
-					: 'files-skeleton'}
-			>
-				{#each SKELETON as i (i)}
-					{#if filesStore.viewMode === 'grid'}
-						<div class="skeleton-card">
-							<div class="skeleton skeleton-thumb"></div>
-							<div class="skeleton skeleton-line skeleton-line--medium"></div>
-							<div class="skeleton skeleton-line skeleton-line--short"></div>
-						</div>
-					{:else}
-						<div class="skeleton-row">
-							<div class="skeleton skeleton-icon"></div>
-							<div class="skeleton skeleton-line skeleton-line--medium"></div>
-							<div class="skeleton skeleton-line skeleton-line--short"></div>
-						</div>
-					{/if}
-				{/each}
-			</div>
-		</div>
+		<SkeletonList count={SKELETON.length} />
 	{:else if isEmpty}
-		<div class="empty-state">
-			<p>{t('files.empty_title', 'This folder is empty')}</p>
-			<p>{t('files.empty_hint', 'Drop files here or use the Upload button to add files.')}</p>
-		</div>
+		<EmptyState
+			title={t('files.empty_title', 'This folder is empty')}
+			hint={t('files.empty_hint', 'Drop files here or use the Upload button to add files.')}
+		/>
 	{:else}
 		<div class="files-container">
 			<div class={viewClass}>
diff --git a/frontend/src/routes/groups/+page.svelte b/frontend/src/routes/groups/+page.svelte
index 92dfe1a6..3cc8f623 100644
--- a/frontend/src/routes/groups/+page.svelte
+++ b/frontend/src/routes/groups/+page.svelte
@@ -1,4 +1,5 @@
 <script lang="ts">
+	import { errorMessage, errorToast } from '$lib/utils/errors';
 	import { onMount } from 'svelte';
 	import {
 		addGroupMember,
@@ -54,7 +55,7 @@
 			groups = page.items;
 			total = page.total;
 		} catch (e) {
-			error = e instanceof Error ? e.message : String(e);
+			error = errorMessage(e);
 		} finally {
 			loading = false;
 		}
@@ -74,7 +75,7 @@
 	}
 
 	function report(e: unknown) {
-		ui.notify(e instanceof Error ? e.message : String(e), 'error');
+		errorToast(e);
 	}
 
 	/** Localised "(N members)" label. Project i18n has no plural rules, so we
diff --git a/frontend/src/routes/music/+page.svelte b/frontend/src/routes/music/+page.svelte
index c8536cf4..43647318 100644
--- a/frontend/src/routes/music/+page.svelte
+++ b/frontend/src/routes/music/+page.svelte
@@ -1,4 +1,6 @@
 <script lang="ts">
+	import { useSelection } from '$lib/composables/useSelection.svelte';
+	import { errorMessage, errorToast } from '$lib/utils/errors';
 	import { onMount } from 'svelte';
 	import { fileInlineUrl } from '$lib/api/endpoints/files';
 	import {
@@ -67,7 +69,7 @@
 			playlists = await listPlaylists();
 			if (!current && playlists.length > 0) await select(playlists[0]);
 		} catch (e) {
-			error = e instanceof Error ? e.message : String(e);
+			error = errorMessage(e);
 		} finally {
 			loading = false;
 		}
@@ -79,7 +81,7 @@
 		try {
 			tracks = await listTracks(p.id);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -95,7 +97,7 @@
 			await select(p);
 			ui.notify(t('music.created', { name: p.name }, 'Created “{{name}}”.'), 'success');
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -112,7 +114,7 @@
 			current.name = name;
 			playlists = playlists.map((p) => (p.id === current!.id ? { ...p, name } : p));
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -131,7 +133,7 @@
 				p.id === current!.id ? { ...p, description: desc || null } : p
 			);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -152,7 +154,7 @@
 			}
 			ui.notify(t('music.deleted', { name: p.name }, 'Deleted “{{name}}”.'), 'success');
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -163,7 +165,7 @@
 			tracks = tracks.filter((x) => x.id !== track.id);
 			ui.notify(t('music.track_removed', 'Track removed.'), 'success');
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -181,7 +183,7 @@
 				'success'
 			);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -207,7 +209,7 @@
 			);
 			ui.notify(t('music.reordered', 'Playlist reordered.'), 'success');
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 			await select(current);
 		}
 	}
@@ -380,7 +382,7 @@
 			);
 			ui.notify(t('music.cover_updated', 'Cover updated.'), 'success');
 		} catch (err) {
-			ui.notify(err instanceof Error ? err.message : String(err), 'error');
+			errorToast(err);
 		}
 	}
 
@@ -406,7 +408,7 @@
 		try {
 			shares = await listShares(current.id);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		} finally {
 			sharesLoading = false;
 		}
@@ -420,7 +422,7 @@
 			await loadShares();
 			ui.notify(t('music.share_added', 'Shared.'), 'success');
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 	async function onRemoveShare(userId: string) {
@@ -429,7 +431,7 @@
 			await removeShare(current.id, userId);
 			await loadShares();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -438,7 +440,7 @@
 	let addOpen = $state(false);
 	let addQuery = $state('');
 	let addResults = $state<FileItem[]>([]);
-	let addSelected = $state<Set<string>>(new Set());
+	const addSelected = useSelection();
 	let addSearching = $state(false);
 	let addDebounce: ReturnType<typeof setTimeout> | null = null;
 
@@ -457,7 +459,7 @@
 					AUDIO_TYPES.some((e) => f.name.toLowerCase().endsWith(`.${e}`))
 			);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 			addResults = [];
 		} finally {
 			addSearching = false;
@@ -471,25 +473,19 @@
 		addOpen = true;
 		addQuery = '';
 		addResults = [];
-		addSelected = new Set();
+		addSelected.clear();
 		void runAddSearch(''); // show all audio files immediately
 	}
-	function toggleAdd(id: string) {
-		const n = new Set(addSelected);
-		if (n.has(id)) n.delete(id);
-		else n.add(id);
-		addSelected = n;
-	}
 	async function confirmAdd() {
 		if (!current || addSelected.size === 0) return;
 		const count = addSelected.size;
 		try {
-			await addTracks(current.id, [...addSelected]);
+			await addTracks(current.id, addSelected.values());
 			addOpen = false;
 			tracks = await listTracks(current.id);
 			ui.notify(t('music.tracks_added', { n: count }, 'Added {{n}} track(s).'), 'success');
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -968,7 +964,7 @@
 							<input
 								type="checkbox"
 								checked={addSelected.has(f.id)}
-								onchange={() => toggleAdd(f.id)}
+								onchange={() => addSelected.toggle(f.id)}
 							/>
 							<Icon name="file-audio" />
 							<span class="music-picker-name" title={f.name}>{f.name}</span>
diff --git a/frontend/src/routes/photos/+page.svelte b/frontend/src/routes/photos/+page.svelte
index 7f4f2b81..d492ad48 100644
--- a/frontend/src/routes/photos/+page.svelte
+++ b/frontend/src/routes/photos/+page.svelte
@@ -1,4 +1,8 @@
 <script lang="ts">
+	import Button from '$lib/components/Button.svelte';
+	import EmptyState from '$lib/components/EmptyState.svelte';
+	import { useSelection } from '$lib/composables/useSelection.svelte';
+	import { errorMessage, errorToast } from '$lib/utils/errors';
 	import { onMount } from 'svelte';
 	import {
 		batchTrash,
@@ -25,7 +29,7 @@
 	type GroupMode = 'day' | 'month' | 'year';
 	const GROUP_KEY = 'oxicloud-photos-group';
 	let groupMode = $state<GroupMode>('month');
-	let selected = $state<Set<string>>(new Set());
+	const selected = useSelection();
 	let lightbox = $state(-1); // index into `items`, -1 = closed
 
 	/** Client-generated video frame thumbnails (file id → data/URL). */
@@ -98,7 +102,7 @@
 			cursor = page.nextCursor;
 			if (!page.nextCursor) exhausted = true;
 		} catch (e) {
-			error = e instanceof Error ? e.message : String(e);
+			error = errorMessage(e);
 			exhausted = true;
 		} finally {
 			loading = false;
@@ -111,21 +115,14 @@
 		if (typeof localStorage !== 'undefined') localStorage.setItem(GROUP_KEY, m);
 	}
 
-	function toggle(id: string) {
-		const n = new Set(selected);
-		if (n.has(id)) n.delete(id);
-		else n.add(id);
-		selected = n;
-	}
-
 	/** A plain tile click toggles selection once anything is selected, else opens the lightbox. */
 	function onTileClick(p: FileItem) {
-		if (selected.size > 0) toggle(p.id);
+		if (selected.size > 0) selected.toggle(p.id);
 		else openLightbox(p);
 	}
 
 	function downloadSelected() {
-		for (const id of selected) {
+		for (const id of selected.ids) {
 			const a = document.createElement('a');
 			a.href = fileDownloadUrl(id);
 			a.download = '';
@@ -136,7 +133,7 @@
 	}
 
 	async function trashSelected() {
-		const ids = [...selected];
+		const ids = selected.values();
 		const ok = await confirmDialog({
 			title: t('photos.delete', 'Delete photos'),
 			message: t('photos.confirm_delete', { n: ids.length }, 'Move {{n}} photos to trash?'),
@@ -148,9 +145,7 @@
 			const trashed = await batchTrash(ids);
 			if (trashed.size > 0) {
 				items = items.filter((p) => !trashed.has(p.id));
-				const n = new Set(selected);
-				for (const id of trashed) n.delete(id);
-				selected = n;
+				for (const id of trashed) selected.delete(id);
 			}
 			if (trashed.size < ids.length) {
 				ui.notify(
@@ -165,7 +160,7 @@
 				ui.notify(t('photos.trashed', { n: trashed.size }, '{{n}} moved to trash.'), 'success');
 			}
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -345,7 +340,7 @@
 			await addFavorite('file', lbItem.id);
 			lbFavorited = !lbFavorited;
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -369,7 +364,7 @@
 				lightbox = Math.min(at, items.length - 1);
 			}
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -422,13 +417,9 @@
 	<div class="batch-bar">
 		<span>{t('files.selected_count', { n: selected.size }, '{{n}} selected')}</span>
 		<div class="batch-bar__actions">
-			<button class="btn btn-secondary" onclick={downloadSelected}
-				>{t('common.download', 'Download')}</button
-			>
-			<button class="btn btn-secondary" onclick={() => (selected = new Set())}
-				>{t('common.clear', 'Clear')}</button
-			>
-			<button class="btn btn-danger" onclick={trashSelected}>{t('common.delete', 'Delete')}</button>
+			<Button onclick={downloadSelected}>{t('common.download', 'Download')}</Button>
+			<Button onclick={() => selected.clear()}>{t('common.clear', 'Clear')}</Button>
+			<Button variant="danger" onclick={trashSelected}>{t('common.delete', 'Delete')}</Button>
 		</div>
 	</div>
 {/if}
@@ -436,13 +427,11 @@
 {#if error}
 	<p class="status status--error" role="alert">{error}</p>
 {:else if items.length === 0 && exhausted}
-	<div class="empty-state">
-		<Icon name="images" class="empty-state__icon" />
-		<p class="empty-state__title">{t('photos.empty', 'No photos yet.')}</p>
-		<p class="empty-state__hint">
-			{t('photos.empty_hint', 'Photos and videos you upload will appear here, grouped by date.')}
-		</p>
-	</div>
+	<EmptyState
+		icon="images"
+		title={t('photos.empty', 'No photos yet.')}
+		hint={t('photos.empty_hint', 'Photos and videos you upload will appear here, grouped by date.')}
+	/>
 {:else}
 	{#each groups as group (group.key)}
 		<h2 class="photos-group">
@@ -473,7 +462,7 @@
 						class="photos__check"
 						class:on={selected.has(photo.id)}
 						aria-label={t('common.select', 'Select')}
-						onclick={() => toggle(photo.id)}
+						onclick={() => selected.toggle(photo.id)}
 					>
 						<Icon name="check" />
 					</button>
@@ -730,32 +719,6 @@
 		color: var(--color-danger-text);
 	}
 
-	.empty-state {
-		display: flex;
-		flex-direction: column;
-		align-items: center;
-		gap: var(--space-2);
-		text-align: center;
-		padding: 4rem 1rem;
-		color: var(--color-text-muted);
-	}
-
-	.empty-state :global(.empty-state__icon) {
-		font-size: 3rem;
-		color: var(--color-text-muted);
-	}
-
-	.empty-state__title {
-		margin: 0;
-		font-size: 1.1rem;
-		color: var(--color-text-heading);
-	}
-
-	.empty-state__hint {
-		margin: 0;
-		max-width: 28rem;
-	}
-
 	.sentinel {
 		height: 1px;
 	}
diff --git a/frontend/src/routes/profile/+page.svelte b/frontend/src/routes/profile/+page.svelte
index bdbd77e1..2dcc824d 100644
--- a/frontend/src/routes/profile/+page.svelte
+++ b/frontend/src/routes/profile/+page.svelte
@@ -1,4 +1,6 @@
 <script lang="ts">
+	import { errorToast } from '$lib/utils/errors';
+	import { relativeTimeAgo } from '$lib/utils/time';
 	import { onMount } from 'svelte';
 	import {
 		changePassword,
@@ -78,26 +80,8 @@
 	const autoPasswords = $derived(appPasswords.filter((p) => isAutoAppPassword(p)));
 
 	/** Relative time (e.g. "3 days ago"); "Never" when absent. */
-	function timeAgo(value: string | null | undefined): string {
-		if (!value) return t('profile.never', 'Never');
-		const date = new Date(value);
-		if (Number.isNaN(date.getTime())) return String(value);
-		const diffSec = Math.round((date.getTime() - Date.now()) / 1000);
-		const abs = Math.abs(diffSec);
-		const rtf = new Intl.RelativeTimeFormat(undefined, { numeric: 'auto' });
-		const units: Array<[Intl.RelativeTimeFormatUnit, number]> = [
-			['year', 31536000],
-			['month', 2592000],
-			['week', 604800],
-			['day', 86400],
-			['hour', 3600],
-			['minute', 60]
-		];
-		for (const [unit, secs] of units) {
-			if (abs >= secs) return rtf.format(Math.round(diffSec / secs), unit);
-		}
-		return rtf.format(diffSec, 'second');
-	}
+	const timeAgo = (value: string | null | undefined): string =>
+		relativeTimeAgo(value, { empty: t('profile.never', 'Never'), invalidAsString: true });
 
 	function hydrate() {
 		const u = session.user;
@@ -139,7 +123,7 @@
 			if (patch.preferred_locale) await setLocale(patch.preferred_locale as Locale);
 			ui.notify(t('profile.saved', 'Profile saved'), 'success');
 		} catch (err) {
-			ui.notify(err instanceof Error ? err.message : String(err), 'error');
+			errorToast(err);
 		} finally {
 			savingProfile = false;
 		}
@@ -164,7 +148,7 @@
 			currentPw = newPw = confirmPw = '';
 			ui.notify(t('profile.password_updated', 'Password updated'), 'success');
 		} catch (err) {
-			ui.notify(err instanceof Error ? err.message : String(err), 'error');
+			errorToast(err);
 		} finally {
 			savingPassword = false;
 		}
@@ -196,7 +180,7 @@
 		} catch (err) {
 			uploadedDataUrl = null;
 			avatarPreview = null;
-			ui.notify(err instanceof Error ? err.message : String(err), 'error');
+			errorToast(err);
 		} finally {
 			input.value = '';
 		}
@@ -210,7 +194,7 @@
 			avatarImgFailed = false;
 			closeAvatarEdit();
 		} catch (err) {
-			ui.notify(err instanceof Error ? err.message : String(err), 'error');
+			errorToast(err);
 		} finally {
 			avatarBusy = false;
 		}
@@ -251,7 +235,7 @@
 			newLabel = '';
 			await loadAppPasswords();
 		} catch (err) {
-			ui.notify(err instanceof Error ? err.message : String(err), 'error');
+			errorToast(err);
 		} finally {
 			creatingPw = false;
 		}
@@ -270,7 +254,7 @@
 			generated = null;
 			await loadAppPasswords();
 		} catch (err) {
-			ui.notify(err instanceof Error ? err.message : String(err), 'error');
+			errorToast(err);
 		}
 	}
 
diff --git a/frontend/src/routes/recent/+page.svelte b/frontend/src/routes/recent/+page.svelte
index 9847f6e6..2205294f 100644
--- a/frontend/src/routes/recent/+page.svelte
+++ b/frontend/src/routes/recent/+page.svelte
@@ -1,4 +1,7 @@
 <script lang="ts">
+	import Button from '$lib/components/Button.svelte';
+	import { useOwnerCache } from '$lib/composables/useOwnerCache.svelte';
+	import { errorToast } from '$lib/utils/errors';
 	import { goto } from '$app/navigation';
 	import { onMount } from 'svelte';
 	import { clearRecent, fetchRecentPage, type RecentResourceItem } from '$lib/api/endpoints/recent';
@@ -14,7 +17,6 @@
 	import { fileDownloadUrl, renameFile, deleteFile } from '$lib/api/endpoints/files';
 	import { renameFolder, deleteFolder } from '$lib/api/endpoints/folders';
 	import type { FileItem, ItemType } from '$lib/api/types';
-	import Icon from '$lib/icons/Icon.svelte';
 	import FileViewer from '$lib/components/FileViewer.svelte';
 	import MoveDialog from '$lib/components/MoveDialog.svelte';
 	import ShareDialog from '$lib/components/ShareDialog.svelte';
@@ -25,7 +27,6 @@
 	} from '$lib/components/ResourceList.svelte';
 	import { confirmDialog, promptDialog } from '$lib/stores/dialogs.svelte';
 	import { t } from '$lib/i18n/index.svelte';
-	import { ui } from '$lib/stores/ui.svelte';
 
 	let raw = $state<RecentResourceItem[]>([]);
 	let cursor = $state<string | undefined>(undefined);
@@ -33,7 +34,7 @@
 	let error = $state<string | null>(null);
 	let groupBy = $state('');
 	let reversed = $state(false);
-	let ownerNames = $state<Record<string, string>>({});
+	const owners = useOwnerCache(resolveOwnerName);
 	let favoriteIds = $state<Set<string>>(new Set());
 
 	const byId = $derived(new Map(raw.map((it) => [it.resource.id, it])));
@@ -51,7 +52,7 @@
 				size: isFile ? (it.resource as FileItem).size : null,
 				date: it.accessed_at,
 				ownerId,
-				ownerName: ownerId ? (ownerNames[ownerId] ?? null) : null,
+				ownerName: owners.name(ownerId),
 				isFavorite: favoriteIds.has(it.resource.id),
 				category: isFile ? it.resource.category : 'Folder',
 				modifiedAt: it.resource.modified_at
@@ -66,7 +67,7 @@
 			label: t('groupby.owner', 'Owner'),
 			orderBy: 'owner',
 			bucketOf: (e) => e.ownerId ?? null,
-			labelOf: (id) => ownerNames[id] ?? id
+			labelOf: (id) => owners.label(id)
 		},
 		{
 			key: 'type',
@@ -95,19 +96,6 @@
 		}
 	];
 
-	async function resolveOwners(items: RecentResourceItem[]) {
-		const ids = [
-			...new Set(items.map((i) => i.resource.owner_id).filter((id): id is string => !!id))
-		];
-		await Promise.all(
-			ids.map(async (id) => {
-				if (ownerNames[id]) return;
-				const name = await resolveOwnerName(id);
-				ownerNames = { ...ownerNames, [id]: name };
-			})
-		);
-	}
-
 	async function loadFavoriteIds() {
 		try {
 			const favs = await fetchFavoritesPage({ resourceTypes: ['file', 'folder'] });
@@ -130,7 +118,7 @@
 			});
 			raw = reset ? page.items : [...raw, ...page.items];
 			cursor = page.next_cursor;
-			void resolveOwners(page.items);
+			void owners.resolve(page.items.map((i) => i.resource.owner_id));
 		} catch (e) {
 			console.error('recent: load error', e);
 			error = t('errors_loadFailed', 'Failed to load items');
@@ -172,7 +160,7 @@
 			favoriteIds = isFav
 				? new Set([...favoriteIds, entry.id])
 				: new Set([...favoriteIds].filter((id) => id !== entry.id));
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -188,7 +176,7 @@
 			raw = [];
 			cursor = undefined;
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -211,7 +199,7 @@
 			else await renameFolder(entry.id, name);
 			await load(true, orderByForGroup());
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -228,7 +216,7 @@
 			else await deleteFolder(entry.id);
 			raw = raw.filter((i) => i.resource.id !== entry.id);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -304,7 +292,7 @@
 			raw = raw.filter((i) => !removed.has(i.resource.id));
 			selectedIds = new Set();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -342,29 +330,22 @@
 >
 	{#snippet toolbar()}
 		{#if entries.length > 0}
-			<button class="btn btn-secondary" onclick={clearAll}>
-				<Icon name="broom" />
-				{t('recent.clear', 'Clear recent')}
-			</button>
+			<Button icon="broom" onclick={clearAll}>{t('recent.clear', 'Clear recent')}</Button>
 		{/if}
 	{/snippet}
 	{#snippet batchToolbar()}
-		<button class="btn btn-secondary" onclick={batchDownload}>
-			<Icon name="download" />
-			{t('common.download', 'Download')}
-		</button>
-		<button
-			class="btn btn-secondary"
+		<Button icon="download" onclick={batchDownload}>{t('common.download', 'Download')}</Button>
+		<Button
+			icon="arrows-alt"
 			onclick={() => {
 				moveTarget = null;
 				moveItems = batchTargets();
 				moveOpen = true;
-			}}><Icon name="arrows-alt" /> {t('files.move', 'Move')}</button
+			}}>{t('files.move', 'Move')}</Button
+		>
+		<Button variant="danger" icon="trash" onclick={batchDelete}
+			>{t('common.delete', 'Delete')}</Button
 		>
-		<button class="btn btn-danger" onclick={batchDelete}>
-			<Icon name="trash" />
-			{t('common.delete', 'Delete')}
-		</button>
 	{/snippet}
 </ResourceList>
 
diff --git a/frontend/src/routes/search/+page.svelte b/frontend/src/routes/search/+page.svelte
index 7202c39f..d0cfc11a 100644
--- a/frontend/src/routes/search/+page.svelte
+++ b/frontend/src/routes/search/+page.svelte
@@ -1,4 +1,6 @@
 <script lang="ts">
+	import EmptyState from '$lib/components/EmptyState.svelte';
+	import { errorMessage } from '$lib/utils/errors';
 	import { goto } from '$app/navigation';
 	import { page } from '$app/state';
 	import { searchFiles } from '$lib/api/endpoints/search';
@@ -142,7 +144,7 @@
 				modifiedAfter: dateBound(dateFilter)
 			});
 		} catch (e) {
-			error = e instanceof Error ? e.message : String(e);
+			error = errorMessage(e);
 		} finally {
 			loading = false;
 		}
@@ -239,16 +241,11 @@
 		</h2>
 	</div>
 {:else if error}
-	<div class="empty-state"><p>{error}</p></div>
+	<EmptyState title={error} error />
 {:else if !query}
-	<div class="empty-state">
-		<p>{t('search.prompt', 'Type a query in the search bar above.')}</p>
-	</div>
+	<EmptyState title={t('search.prompt', 'Type a query in the search bar above.')} />
 {:else if isEmpty}
-	<div class="empty-state search-empty">
-		<Icon name="search" />
-		<p>{t('search.no_results', 'No results found for this search')}</p>
-	</div>
+	<EmptyState icon="search" title={t('search.no_results', 'No results found for this search')} />
 {:else if results}
 	<div class="files-container">
 		<div class="files-list-view" style="--files-list-columns: minmax(200px, 2fr) 1fr 110px 140px">
@@ -383,16 +380,4 @@
 		font-weight: var(--weight-medium);
 		color: var(--color-text);
 	}
-
-	.search-empty {
-		display: flex;
-		flex-direction: column;
-		align-items: center;
-		gap: var(--space-3);
-	}
-
-	.search-empty :global(.oxi-icon) {
-		font-size: var(--text-3xl);
-		color: var(--color-text-faint);
-	}
 </style>
diff --git a/frontend/src/routes/shared-with-me/+page.svelte b/frontend/src/routes/shared-with-me/+page.svelte
index 136af52a..ab101b80 100644
--- a/frontend/src/routes/shared-with-me/+page.svelte
+++ b/frontend/src/routes/shared-with-me/+page.svelte
@@ -1,4 +1,5 @@
 <script lang="ts">
+	import { errorMessage } from '$lib/utils/errors';
 	import { goto } from '$app/navigation';
 	import { onMount } from 'svelte';
 	import { fetchSharedWithMe, type IncomingGrantItem } from '$lib/api/endpoints/grants';
@@ -38,7 +39,7 @@
 			raw = reset ? page.items : [...raw, ...page.items];
 			cursor = page.next_cursor;
 		} catch (e) {
-			error = e instanceof Error ? e.message : String(e);
+			error = errorMessage(e);
 		} finally {
 			loading = false;
 		}
diff --git a/frontend/src/routes/shared/+page.svelte b/frontend/src/routes/shared/+page.svelte
index f92ddc4f..a86ba371 100644
--- a/frontend/src/routes/shared/+page.svelte
+++ b/frontend/src/routes/shared/+page.svelte
@@ -1,4 +1,6 @@
 <script lang="ts">
+	import EmptyState from '$lib/components/EmptyState.svelte';
+	import { errorMessage, errorToast } from '$lib/utils/errors';
 	import { goto } from '$app/navigation';
 	import { onMount } from 'svelte';
 	import {
@@ -152,7 +154,7 @@
 			raw = reset ? page.items : [...raw, ...page.items];
 			cursor = page.next_cursor;
 		} catch (e) {
-			error = e instanceof Error ? e.message : String(e);
+			error = errorMessage(e);
 		} finally {
 			loading = false;
 		}
@@ -232,7 +234,7 @@
 			g.role = role;
 			raw = [...raw];
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -248,7 +250,7 @@
 			g.expires_at = iso;
 			raw = [...raw];
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -257,7 +259,7 @@
 		try {
 			summarize((await notifyGrantRecipient(g.grant_id)).outcomes);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -267,7 +269,7 @@
 			await revokeGrant(g.grant_id);
 			dropGrant(g.grant_id);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -278,7 +280,7 @@
 			if (await copyShareLink(share.url)) ui.notify(t('share.copied', 'Link copied'), 'success');
 			else ui.notify(t('share.copy_failed', 'Could not copy link'), 'error');
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -288,7 +290,7 @@
 			g.expires_at = expiryToIso(date || null);
 			raw = [...raw];
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -311,7 +313,7 @@
 				'success'
 			);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -321,7 +323,7 @@
 			await deleteShare(g.subject_id);
 			dropGrant(g.grant_id);
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -363,18 +365,13 @@
 </div>
 
 {#if error}
-	<div class="empty-state">
-		<Icon name="exclamation-circle" class="empty-state-icon empty-state-icon--error" />
-		<p>{error}</p>
-	</div>
+	<EmptyState icon="exclamation-circle" title={error} error />
 {:else if isEmpty}
-	<div class="empty-state">
-		<Icon name="share-alt" class="empty-state-icon" />
-		<p>{t('myshares.emptyStateTitle', "You haven't shared anything yet")}</p>
-		<p class="empty-state__hint">
-			{t('myshares.emptyStateDesc', 'Items you share with others will appear here')}
-		</p>
-	</div>
+	<EmptyState
+		icon="share-alt"
+		title={t('myshares.emptyStateTitle', "You haven't shared anything yet")}
+		hint={t('myshares.emptyStateDesc', 'Items you share with others will appear here')}
+	/>
 {:else}
 	<div class="ms-lanes">
 		{#each lanes as lane (lane.key)}
@@ -832,19 +829,4 @@
 	.ms-more {
 		margin: var(--space-3) auto 0;
 	}
-
-	.empty-state__hint {
-		color: var(--color-text-muted);
-		font-size: var(--text-sm);
-	}
-
-	.empty-state :global(.empty-state-icon) {
-		font-size: var(--text-5xl);
-		color: var(--color-text-faint);
-		margin-bottom: var(--space-2);
-	}
-
-	.empty-state :global(.empty-state-icon--error) {
-		color: var(--color-danger-text);
-	}
 </style>
diff --git a/frontend/src/routes/trash/+page.svelte b/frontend/src/routes/trash/+page.svelte
index a1d4f0c0..1cbb3b01 100644
--- a/frontend/src/routes/trash/+page.svelte
+++ b/frontend/src/routes/trash/+page.svelte
@@ -1,4 +1,5 @@
 <script lang="ts">
+	import { errorToast } from '$lib/utils/errors';
 	import { onMount } from 'svelte';
 	import {
 		deleteTrashItem,
@@ -110,7 +111,7 @@
 			ui.notify(t('trash.restored', 'Restored'), 'success');
 			await reloadFromTop();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -126,7 +127,7 @@
 			await deleteTrashItem(entry.id);
 			await reloadFromTop();
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}
 
@@ -143,7 +144,7 @@
 			raw = [];
 			cursor = undefined;
 		} catch (e) {
-			ui.notify(e instanceof Error ? e.message : String(e), 'error');
+			errorToast(e);
 		}
 	}