feat(eq): android auto custom equalizer and robust device detection

- MainActivity: onListen re-emits the current active device and registers
  the audio device callback idempotently, so recreated activities resync
  instead of freezing the active-device id on a disconnected device.
- servicio_dispositivo_audio: resubscribir() re-opens the event channel;
  estado_ecualizador exposes refrescarDispositivoActual() with an
  in-flight guard, invoked on app resume and when opening advanced EQ
  options, clearing stale green-dot device selections.
- navegacion_auto/servicio_audio: new 'Personalizado' browse tree in
  Android Auto (5 band folders, 13 gain steps each) applied live via
  setBanda; preset and gain taps persist at device level when
  multi-device EQ is active and respect station/matrix overrides,
  with apply-before-persist ordering and children-changed notifications.
- l10n: regenerate stale generated localizations; add rxdart as direct
  dependency for the subscribeToChildren override.

lib/l10n/gen/app_localizations_ja.dart

@@ -62,22 +62,22 @@ class AppLocalizationsJa extends AppLocalizations {
     Object minutes,
     Object seconds,
   ) {
-    return '$hours?? $minutes? $seconds?';
+    return '$hours時間$minutes分$seconds秒';
   }
 
   @override
   String durationMinutesSeconds(Object minutes, Object seconds) {
-    return '$minutes? $seconds?';
+    return '$minutes分$seconds秒';
   }
 
   @override
   String durationMinutesOnly(Object minutes) {
-    return '$minutes?';
+    return '$minutes分';
   }
 
   @override
   String durationSecondsOnly(Object seconds) {
-    return '$seconds?';
+    return '$seconds秒';
   }
 
   @override
@@ -1263,4 +1263,34 @@ class AppLocalizationsJa extends AppLocalizations {
 
   @override
   String get eqDeviceConnected => '接続中';
+
+  @override
+  String get localMusicSectionTitle => 'ローカル音楽（Android Auto）';
+
+  @override
+  String get localMusicSectionDescription =>
+      'この端末のフォルダーを選択して、車内でその音声ファイルを閲覧・再生します。';
+
+  @override
+  String get localMusicFolderNotConfigured => 'フォルダーが選択されていません';
+
+  @override
+  String get localMusicFolderTitle => 'ローカル音楽フォルダー';
+
+  @override
+  String get localMusicChoosePath => 'フォルダーを選択';
+
+  @override
+  String get localMusicChangePath => 'フォルダーを変更';
+
+  @override
+  String get localMusicFolderUpdated => 'ローカル音楽フォルダーを更新しました';
+
+  @override
+  String localMusicFolderSaveError(Object error) {
+    return 'フォルダーを保存できませんでした: $error';
+  }
+
+  @override
+  String get localMusicFolderGenericName => '選択したフォルダー';
 }