Port of the explicit-content indicator from SpotiFLAC-Web (issue #456):
- Go: add explicit to ExtTrackMetadata (parsed generically from any
extension via explicit/is_explicit/isExplicit), TrackMetadata, and
AlbumTrackMetadata; built-in Deezer maps explicit_lyrics and
explicit_content_lyrics == 1
- Dart: add explicit to the Track model with a tolerant
parseExplicitFlag helper wired into all backend track parsers
- UI: new ExplicitBadge rendered through buildQualityBadges on album,
playlist, search, and home track rows
- Add homeFeedProvider field to AppSettings with picker UI in extensions page
- Update explore_provider to respect user's home feed provider preference
- Add normalizeCoverReference() and normalizeRemoteHttpUrl() to filter
invalid cover URLs (no scheme, no host, protocol-relative)
- Apply cover URL normalization across all screens and providers to
prevent 'no host specified in URI' errors from Qobuz
- Propagate CoverURL from QobuzDownloadResult through Go backend so
cover art is available even when request metadata is incomplete
- Extract normalizeOptionalString() to lib/utils/string_utils.dart from download_queue_provider and track_metadata_screen
- Extract PrioritySettingsScaffold widget from lyrics and metadata priority pages, reducing ~280 lines of duplication
- Extract _ensureDefaultDocumentsOutputDir/_ensureDefaultAndroidMusicOutputDir in download queue provider
- Extract collectLibraryAudioFiles() and applyDefaultLibraryMetadata() in Go library_scan.go
- Extract plainTextLyricsLines() in Go lyrics.go, used by Apple Music, Musixmatch, and QQ Music clients
zarzet