feat: YouTube customizable bitrate, improved title matching, SpotubeDL engine fallback

- Add configurable YouTube Opus (96-256kbps) and MP3 (96-320kbps) bitrates
- Improve title matching with loose normalization for symbol-heavy tracks
- Add SpotubeDL engine v2 fallback for MP3 requests
- Improve filename sanitization in track metadata screen
- Bump version to 3.6.9+82

lib/providers/download_queue_provider.dart

@@ -2771,7 +2771,29 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
         settings,
       );
 
-      final quality = item.qualityOverride ?? state.audioQuality;
+      var quality = item.qualityOverride ?? state.audioQuality;
+      if (item.service.toLowerCase() == 'youtube') {
+        final normalized = quality.toLowerCase();
+        final isYoutubeQuality =
+            normalized.startsWith('mp3_') || normalized.startsWith('opus_');
+        if (!isYoutubeQuality) {
+          final mp3Bitrate = (() {
+            const supported = [128, 256, 320];
+            var nearest = supported.first;
+            var nearestDistance = (settings.youtubeMp3Bitrate - nearest).abs();
+            for (final option in supported.skip(1)) {
+              final distance = (settings.youtubeMp3Bitrate - option).abs();
+              if (distance < nearestDistance ||
+                  (distance == nearestDistance && option > nearest)) {
+                nearest = option;
+                nearestDistance = distance;
+              }
+            }
+            return nearest;
+          })();
+          quality = 'mp3_$mp3Bitrate';
+        }
+      }
       final isSafMode = _isSafMode(settings);
       final relativeOutputDir = isSafMode
           ? await _buildRelativeOutputDir(
@@ -3032,8 +3054,7 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
           outputDir: outputDir,
           filenameFormat: state.filenameFormat,
           quality: quality,
-          // Keep prior behavior: non-YouTube paths were implicitly true.
-          embedLyrics: isYouTube ? settings.embedLyrics : true,
+          embedLyrics: settings.embedLyrics,
           embedMaxQualityCover: settings.maxQualityCover,
           trackNumber: normalizedTrackNumber,
           discNumber: normalizedDiscNumber,

lib/providers/settings_provider.dart

@@ -13,6 +13,9 @@ const _spotifyClientSecretKey = 'spotify_client_secret';
 final _log = AppLogger('SettingsProvider');
 
 class SettingsNotifier extends Notifier<AppSettings> {
+  static const List<int> _youtubeOpusSupportedBitrates = [128, 256];
+  static const List<int> _youtubeMp3SupportedBitrates = [128, 256, 320];
+
   final Future<SharedPreferences> _prefs = SharedPreferences.getInstance();
   final FlutterSecureStorage _secureStorage = const FlutterSecureStorage();
   bool _isSavingSettings = false;
@@ -32,6 +35,7 @@ class SettingsNotifier extends Notifier<AppSettings> {
       state = AppSettings.fromJson(jsonDecode(json));
 
       await _runMigrations(prefs);
+      await _normalizeYouTubeBitratesIfNeeded();
     }
 
     await _loadSpotifyClientSecret(prefs);
@@ -107,6 +111,49 @@ class SettingsNotifier extends Notifier<AppSettings> {
     }
   }
 
+  int _nearestSupportedBitrate(int value, List<int> supported) {
+    var nearest = supported.first;
+    var nearestDistance = (value - nearest).abs();
+
+    for (final option in supported.skip(1)) {
+      final distance = (value - option).abs();
+      // On tie, prefer higher quality bitrate.
+      if (distance < nearestDistance ||
+          (distance == nearestDistance && option > nearest)) {
+        nearest = option;
+        nearestDistance = distance;
+      }
+    }
+
+    return nearest;
+  }
+
+  int _normalizeYouTubeOpusBitrate(int bitrate) {
+    return _nearestSupportedBitrate(bitrate, _youtubeOpusSupportedBitrates);
+  }
+
+  int _normalizeYouTubeMp3Bitrate(int bitrate) {
+    return _nearestSupportedBitrate(bitrate, _youtubeMp3SupportedBitrates);
+  }
+
+  Future<void> _normalizeYouTubeBitratesIfNeeded() async {
+    final normalizedOpus = _normalizeYouTubeOpusBitrate(
+      state.youtubeOpusBitrate,
+    );
+    final normalizedMp3 = _normalizeYouTubeMp3Bitrate(state.youtubeMp3Bitrate);
+
+    if (normalizedOpus == state.youtubeOpusBitrate &&
+        normalizedMp3 == state.youtubeMp3Bitrate) {
+      return;
+    }
+
+    state = state.copyWith(
+      youtubeOpusBitrate: normalizedOpus,
+      youtubeMp3Bitrate: normalizedMp3,
+    );
+    await _saveSettings();
+  }
+
   Future<void> _loadSpotifyClientSecret(SharedPreferences prefs) async {
     final storedSecret = await _secureStorage.read(
       key: _spotifyClientSecretKey,
@@ -230,7 +277,9 @@ class SettingsNotifier extends Notifier<AppSettings> {
   }
 
   void setMusixmatchLanguage(String languageCode) {
-    state = state.copyWith(musixmatchLanguage: languageCode.trim().toLowerCase());
+    state = state.copyWith(
+      musixmatchLanguage: languageCode.trim().toLowerCase(),
+    );
     _saveSettings();
     _syncLyricsSettingsToBackend();
   }
@@ -390,6 +439,18 @@ class SettingsNotifier extends Notifier<AppSettings> {
     _saveSettings();
   }
 
+  void setYoutubeOpusBitrate(int bitrate) {
+    final normalized = _normalizeYouTubeOpusBitrate(bitrate);
+    state = state.copyWith(youtubeOpusBitrate: normalized);
+    _saveSettings();
+  }
+
+  void setYoutubeMp3Bitrate(int bitrate) {
+    final normalized = _normalizeYouTubeMp3Bitrate(bitrate);
+    state = state.copyWith(youtubeMp3Bitrate: normalized);
+    _saveSettings();
+  }
+
   void setUseAllFilesAccess(bool enabled) {
     state = state.copyWith(useAllFilesAccess: enabled);
     _saveSettings();