feat(multi-select): Phase 1 - FavoritesView track multi-select

- Add BulkActionBar component (sticky-bottom bar with queue split button,
  add to playlist, add to favorites, clear selection)
- Add selectable/selected/onToggleSelect props to TrackRow with checkbox UI
- Add .selected highlight and .track-checkbox CSS to TrackRow
- Extend VirtualizedTrackList with selectable/selectedIds/onToggleSelect props
- Wire FavoritesView tracks tab: Select toggle button in toolbar,
  selectedTrackIds state, BulkActionBar with bulk queue/favorites/playlist handlers
- Add actions.select and actions.cancelSelection i18n keys to all 4 locales

src/lib/i18n/locales/fr.json

@@ -506,6 +506,10 @@
     "addToPlaylist": "Ajouter à la playlist",
     "addToFavorites": "Ajouter aux favoris",
     "removeFromFavorites": "Retirer des favoris",
+    "removeFromPlaylist": "Retirer de la playlist",
+    "selectedTracks": "{count, plural, one {# titre sélectionné} other {# titres sélectionnés}}",
+    "select": "Sélectionner",
+    "cancelSelection": "Annuler la sélection",
     "makeAvailableOffline": "Rendre disponible hors ligne",
     "share": "Partager",
     "viewAlbum": "Voir l'album",