feat: add AAC lossy target and toggle for Apple Music eLRC word sync

The HIGH-quality lossy format picker can now produce an AAC/M4A 320 kbps output alongside MP3 and Opus. FFmpegService.convertM4aToLossy/convertAudioFormat, the Dart queue pipeline, the Kotlin finalizer, and the library database format helper all route .m4a through a unified aac codec path and tag the resulting file with the M4A metadata writer. The Lossy Format setting gains a new option, and the track metadata convert dialog lists AAC next to the other targets.

Apple Music lyrics gain a 'eLRC word sync' switch (default off). When disabled the pax-to-LRC formatter strips inline word timestamps, producing line-synced LRC that is safer for players that choke on eLRC; enabling it restores the previous word-by-word behaviour. The change propagates through SetLyricsFetchOptions and invalidates the global lyrics cache on toggle.

Broad l10n migration: roughly 400 previously hardcoded English strings across queue, settings, track metadata, repo, audio analysis, setup and extension screens now live in the ARB catalog, with matching plural/placeholder forms. No behaviour change beyond localisation. Existing and new unit tests (lyrics eLRC toggle and Dart settings round-trip) pass.

lib/models/settings.dart

@@ -47,7 +47,7 @@ class AppSettings {
   final String locale;
   final String lyricsMode;
   final String
-  tidalHighFormat; // Format for Tidal HIGH quality: 'mp3_320', 'opus_256', or 'opus_128'
+  tidalHighFormat; // Format for Tidal HIGH quality: 'mp3_320', 'aac_320', 'opus_256', or 'opus_128'
   final bool
   useAllFilesAccess; // Android 13+ only: enable MANAGE_EXTERNAL_STORAGE
   final bool
@@ -81,6 +81,8 @@ class AppSettings {
   lyricsIncludeRomanizationNetease; // Append romanized lyrics (Netease)
   final bool
   lyricsMultiPersonWordByWord; // Enable v1/v2 + [bg:] tags for Apple/QQ syllable lyrics
+  final bool
+  lyricsAppleElrcWordSync; // Preserve Apple Music inline word timestamps for eLRC-capable players
   final String
   musixmatchLanguage; // Optional ISO language code for Musixmatch localized lyrics
 
@@ -146,6 +148,7 @@ class AppSettings {
     this.lyricsIncludeTranslationNetease = false,
     this.lyricsIncludeRomanizationNetease = false,
     this.lyricsMultiPersonWordByWord = false,
+    this.lyricsAppleElrcWordSync = false,
     this.musixmatchLanguage = '',
     this.lastSeenVersion = '',
     this.deduplicateDownloads = true,
@@ -210,6 +213,7 @@ class AppSettings {
     bool? lyricsIncludeTranslationNetease,
     bool? lyricsIncludeRomanizationNetease,
     bool? lyricsMultiPersonWordByWord,
+    bool? lyricsAppleElrcWordSync,
     String? musixmatchLanguage,
     String? lastSeenVersion,
     bool? deduplicateDownloads,
@@ -291,6 +295,8 @@ class AppSettings {
           this.lyricsIncludeRomanizationNetease,
       lyricsMultiPersonWordByWord:
           lyricsMultiPersonWordByWord ?? this.lyricsMultiPersonWordByWord,
+      lyricsAppleElrcWordSync:
+          lyricsAppleElrcWordSync ?? this.lyricsAppleElrcWordSync,
       musixmatchLanguage: musixmatchLanguage ?? this.musixmatchLanguage,
       lastSeenVersion: lastSeenVersion ?? this.lastSeenVersion,
       deduplicateDownloads: deduplicateDownloads ?? this.deduplicateDownloads,

lib/models/settings.g.dart

@@ -78,6 +78,7 @@ AppSettings _$AppSettingsFromJson(Map<String, dynamic> json) => AppSettings(
       json['lyricsIncludeRomanizationNetease'] as bool? ?? false,
   lyricsMultiPersonWordByWord:
       json['lyricsMultiPersonWordByWord'] as bool? ?? false,
+  lyricsAppleElrcWordSync: json['lyricsAppleElrcWordSync'] as bool? ?? false,
   musixmatchLanguage: json['musixmatchLanguage'] as String? ?? '',
   lastSeenVersion: json['lastSeenVersion'] as String? ?? '',
   deduplicateDownloads: json['deduplicateDownloads'] as bool? ?? true,
@@ -142,6 +143,7 @@ Map<String, dynamic> _$AppSettingsToJson(
   'lyricsIncludeTranslationNetease': instance.lyricsIncludeTranslationNetease,
   'lyricsIncludeRomanizationNetease': instance.lyricsIncludeRomanizationNetease,
   'lyricsMultiPersonWordByWord': instance.lyricsMultiPersonWordByWord,
+  'lyricsAppleElrcWordSync': instance.lyricsAppleElrcWordSync,
   'musixmatchLanguage': instance.musixmatchLanguage,
   'lastSeenVersion': instance.lastSeenVersion,
   'deduplicateDownloads': instance.deduplicateDownloads,