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/routes/+layout.svelte

@@ -2,6 +2,7 @@
 	import { onMount } from 'svelte';
 	import '../app.css';
 	import IconSprite from '$lib/components/IconSprite.svelte';
+	import ContextMenu from '$lib/components/ContextMenu.svelte';
 	import { auth } from '$lib/stores/auth.svelte';
 	import { theme } from '$lib/stores/theme.svelte';
 	import { density } from '$lib/stores/density.svelte';
@@ -23,3 +24,4 @@
 
 <IconSprite />
 {@render children()}
+<ContextMenu />