- 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)