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.dart

@@ -2395,6 +2395,60 @@ abstract class AppLocalizations {
   /// In es, this message translates to:
   /// **'Conectado'**
   String get eqDeviceConnected;
+
+  /// No description provided for @localMusicSectionTitle.
+  ///
+  /// In es, this message translates to:
+  /// **'Música local (Android Auto)'**
+  String get localMusicSectionTitle;
+
+  /// No description provided for @localMusicSectionDescription.
+  ///
+  /// In es, this message translates to:
+  /// **'Elegí una carpeta de este dispositivo para explorar y reproducir sus archivos de audio desde el auto.'**
+  String get localMusicSectionDescription;
+
+  /// No description provided for @localMusicFolderNotConfigured.
+  ///
+  /// In es, this message translates to:
+  /// **'No hay carpeta seleccionada'**
+  String get localMusicFolderNotConfigured;
+
+  /// No description provided for @localMusicFolderTitle.
+  ///
+  /// In es, this message translates to:
+  /// **'Carpeta de música local'**
+  String get localMusicFolderTitle;
+
+  /// No description provided for @localMusicChoosePath.
+  ///
+  /// In es, this message translates to:
+  /// **'Elegir carpeta'**
+  String get localMusicChoosePath;
+
+  /// No description provided for @localMusicChangePath.
+  ///
+  /// In es, this message translates to:
+  /// **'Cambiar carpeta'**
+  String get localMusicChangePath;
+
+  /// No description provided for @localMusicFolderUpdated.
+  ///
+  /// In es, this message translates to:
+  /// **'Carpeta de música local actualizada'**
+  String get localMusicFolderUpdated;
+
+  /// No description provided for @localMusicFolderSaveError.
+  ///
+  /// In es, this message translates to:
+  /// **'No se pudo guardar la carpeta: {error}'**
+  String localMusicFolderSaveError(Object error);
+
+  /// No description provided for @localMusicFolderGenericName.
+  ///
+  /// In es, this message translates to:
+  /// **'Carpeta seleccionada'**
+  String get localMusicFolderGenericName;
 }
 
 class _AppLocalizationsDelegate