feat: context menus, unified photo panel, tags, album trash and counters

- backend: deleting an album moves its photos to the trash without losing files (photos.album_id nullable, FK ON DELETE SET NULL, migration 000006; dropped S3 prefix delete); restore accepts an album target (album_required when the album is gone); user-scoped tags (000007) with GET /tags, POST/DELETE /photos/:id/tags, tags included in photo responses; GET /trash/count
- frontend: right-click context menus for photos (grid + viewer) and albums (rail + overview); single shared PhotoPanel reused in viewer and gallery selection (not a copy); viewer download/delete moved to the panel 'Действия'; transparent compact viewer top bar; trash entry as last rail item with per-album photo counts and trash count; album rename/delete dialogs
- openspec: sync lightroom-workspace-ui artifacts (specs photos/ui-workspace, design #24-30, tasks 9.17-9.24)

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

@@ -0,0 +1,24 @@
+import { photosApi } from '$lib/api';
+import { auth } from './auth.svelte';
+
+class TrashStore {
+	count = $state(0);
+
+	async load() {
+		if (!auth.isAuthenticated) {
+			this.count = 0;
+			return;
+		}
+		try {
+			this.count = (await photosApi.trashCount()).count;
+		} catch {
+			/* ignore */
+		}
+	}
+
+	reset() {
+		this.count = 0;
+	}
+}
+
+export const trash = new TrashStore();