- Add CollectionArtistEntry model with toJson/fromJson and artistCollectionKey helper
- Create favorite_artists table in SQLite with DB migration v1→v2
- Implement toggleFavoriteArtist/removeFavoriteArtist in LibraryCollectionsNotifier
- Add FavoriteArtistsScreen with list view, empty state, and artist navigation
- Add heart toggle button on ArtistScreen header (reactive via Riverpod selector)
- Integrate favorite artists folder in queue_tab collection grid/list views
- Add 8 new localization strings across all 13 locale files
- Extract home_tab.dart helpers/widgets into home_tab_helpers.dart and home_tab_widgets.dart using Dart part files
- Extract queue_tab.dart helpers/widgets into queue_tab_helpers.dart and queue_tab_widgets.dart using Dart part files
- Extract track_metadata_edit_sheet.dart from track_metadata_screen.dart using Dart part file
- Refactor _FileExistsListenableCache into a standalone class in queue_tab_helpers.dart
- Fix artist_screen.dart: replace unreliable findAncestorStateOfType with GlobalKey for _FetchingProgressDialog progress updates
- DRY platform_bridge.dart: extract common JSON decode patterns into reusable helper methods (_decodeRequiredMapResult, _decodeNullableMapResult, _decodeMapListResult, _decodeStringListResult)