feat(ui): show a notification if user try to drop a file in another section than /files

frontend/src/lib/components/ResourceList.svelte

@@ -92,6 +92,8 @@
 	import DisplayModeControls from '$lib/components/DisplayModeControls.svelte';
 	import UserVignette from '$lib/components/UserVignette.svelte';
 	import VirtualList from '$lib/components/VirtualList.svelte';
+	import { goto } from '$app/navigation';
+	import { resolve } from '$app/paths';
 	import { t } from '$lib/i18n/index.svelte';
 	import { ui } from '$lib/stores/ui.svelte';
 	import { files as filesStore } from '$lib/stores/files.svelte';
@@ -927,7 +929,13 @@
 		// element accepts drops — without it, `drop` never fires and
 		// the pointer shows the OS "no-drop" cursor.
 		e.preventDefault();
-		if (e.dataTransfer) e.dataTransfer.dropEffect = enableSystemDrop ? 'copy' : 'none';
+		// `dropEffect = 'none'` would tell the browser to REJECT the
+		// drop before `drop` fires — the toast/notification path in
+		// `onSystemDrop` would never run for wrong-zone drops. Always
+		// accept at the pointer level; the drop handler decides
+		// whether to upload (`enableSystemDrop`) or fire the
+		// "go to Files" toast.
+		if (e.dataTransfer) e.dataTransfer.dropEffect = 'copy';
 	}
 	function onSystemDragLeave(e: DragEvent) {
 		if (!isSystemDrag(e)) return;
@@ -949,7 +957,19 @@
 					'Uploads only work in Files — open the Files section and drop there.'
 				),
 				'warning',
-				6000
+				6000,
+				true,
+				{
+					action: {
+						label: t('resource_list.wrong_drop_zone_action', 'Go to Files'),
+						// One-click recovery from a mis-drop: land the user in
+						// /files so they can re-drag from the OS. We don't
+						// re-attach the dropped files (browsers throw away
+						// DataTransfer once the drop event returns), so this
+						// is the best we can offer without a second drag.
+						onClick: () => goto(resolve('/files'))
+					}
+				}
 			);
 		}
 	}

frontend/src/lib/components/Toaster.svelte

@@ -12,6 +12,18 @@
 	{#each ui.toasts as toast (toast.id)}
 		<div class="toast toast--{toast.kind}" role="status" data-testid={`toaster-toast-${toast.id}`}>
 			<span class="toast__msg">{toast.message}</span>
+			{#if toast.action}
+				<button
+					class="toast__action"
+					data-testid={`toaster-action-btn-${toast.id}`}
+					onclick={() => {
+						toast.action?.onClick();
+						ui.dismiss(toast.id);
+					}}
+				>
+					{toast.action.label}
+				</button>
+			{/if}
 			<button
 				class="toast__close"
 				data-testid={`toaster-dismiss-btn-${toast.id}`}
@@ -73,6 +85,22 @@
 		flex: 1;
 	}
 
+	.toast__action {
+		flex-shrink: 0;
+		background: var(--color-accent);
+		color: var(--color-accent-contrast);
+		border: none;
+		border-radius: var(--radius-md);
+		padding: var(--space-1-5) var(--space-3);
+		font-size: var(--text-sm);
+		font-weight: var(--weight-medium);
+		cursor: pointer;
+	}
+
+	.toast__action:hover {
+		filter: brightness(0.95);
+	}
+
 	.toast__close {
 		background: none;
 		border: none;

frontend/src/lib/stores/ui.svelte.ts

@@ -6,10 +6,19 @@
  */
 export type ToastKind = 'info' | 'success' | 'error' | 'warning';
 
+export interface ToastAction {
+	/** Button label — should be short (≤ 20 chars). */
+	label: string;
+	/** Invoked when the button is clicked; the toast auto-dismisses after. */
+	onClick: () => void;
+}
+
 export interface Toast {
 	id: number;
 	message: string;
 	kind: ToastKind;
+	/** Optional inline action (e.g. "Go to Files" on a wrong-drop-zone toast). */
+	action?: ToastAction;
 }
 
 export interface Notification {
@@ -74,10 +83,21 @@ class UiStore {
 	/**
 	 * Raise a toast and record a notification. `at` is stamped from the clock at
 	 * call time; pass `record: false` for purely transient messages.
+	 *
+	 * The optional `opts.action` renders an inline button in the toast (e.g.
+	 * "Go to Files" on a wrong-drop-zone warning); the callback fires on
+	 * click and the toast auto-dismisses right after so a caller doesn't have
+	 * to manage the id.
 	 */
-	notify(message: string, kind: ToastKind = 'info', timeoutMs = 4000, record = true): number {
+	notify(
+		message: string,
+		kind: ToastKind = 'info',
+		timeoutMs = 4000,
+		record = true,
+		opts: { action?: ToastAction } = {}
+	): number {
 		const id = ++this.#seq;
-		this.toasts = [...this.toasts, { id, message, kind }];
+		this.toasts = [...this.toasts, { id, message, kind, action: opts.action }];
 		if (record) {
 			this.notifications = [
 				{ id, message, kind, at: Date.now(), read: false },