feat: Immich album linking with auto-sync (#206)

- Link Immich albums to trips — photos sync automatically
- Album picker shows all user's Immich albums
- Linked albums displayed as chips with sync/unlink buttons
- Auto-sync on link: fetches all album photos and adds to trip
- Manual re-sync button for each linked album
- DB migration: trip_album_links table

fix: shared Immich photos visible to other trip members

- Thumbnail/original proxy now uses photo owner's Immich credentials
  when userId query param is provided, fixing 404 for shared photos
- i18n: album keys for all 12 languages

client/src/i18n/translations/de.ts

@@ -1344,6 +1344,12 @@ const de: Record<string, string | { name: string; category: string }[]> = {
   'memories.connectionError': 'Verbindung zu Immich fehlgeschlagen',
   'memories.saved': 'Immich-Einstellungen gespeichert',
   'memories.addPhotos': 'Fotos hinzufügen',
+  'memories.linkAlbum': 'Album verknüpfen',
+  'memories.selectAlbum': 'Immich-Album auswählen',
+  'memories.noAlbums': 'Keine Alben gefunden',
+  'memories.syncAlbum': 'Album synchronisieren',
+  'memories.unlinkAlbum': 'Album trennen',
+  'memories.photos': 'Fotos',
   'memories.selectPhotos': 'Fotos aus Immich auswählen',
   'memories.selectHint': 'Tippe auf Fotos um sie auszuwählen.',
   'memories.selected': 'ausgewählt',