init new frontend

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

@@ -0,0 +1,32 @@
+/**
+ * Transient UI state — toasts now; cross-component dialog targets are added as
+ * the views that need them land (Phases 2–4). Component-local state is preferred;
+ * only state that must cross component boundaries belongs here.
+ */
+export type ToastKind = 'info' | 'success' | 'error' | 'warning';
+
+export interface Toast {
+	id: number;
+	message: string;
+	kind: ToastKind;
+}
+
+class UiStore {
+	toasts = $state<Toast[]>([]);
+	#seq = 0;
+
+	notify(message: string, kind: ToastKind = 'info', timeoutMs = 4000): number {
+		const id = ++this.#seq;
+		this.toasts = [...this.toasts, { id, message, kind }];
+		if (timeoutMs > 0 && typeof setTimeout !== 'undefined') {
+			setTimeout(() => this.dismiss(id), timeoutMs);
+		}
+		return id;
+	}
+
+	dismiss(id: number): void {
+		this.toasts = this.toasts.filter((t) => t.id !== id);
+	}
+}
+
+export const ui = new UiStore();