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_id.dart

@@ -1309,4 +1309,34 @@ class AppLocalizationsId extends AppLocalizations {
 
   @override
   String get eqDeviceConnected => 'Terhubung';
+
+  @override
+  String get localMusicSectionTitle => 'Musik lokal (Android Auto)';
+
+  @override
+  String get localMusicSectionDescription =>
+      'Pilih folder di perangkat ini untuk menjelajahi dan memutar file audio di dalamnya dari mobil.';
+
+  @override
+  String get localMusicFolderNotConfigured => 'Belum ada folder dipilih';
+
+  @override
+  String get localMusicFolderTitle => 'Folder musik lokal';
+
+  @override
+  String get localMusicChoosePath => 'Pilih folder';
+
+  @override
+  String get localMusicChangePath => 'Ubah folder';
+
+  @override
+  String get localMusicFolderUpdated => 'Folder musik lokal diperbarui';
+
+  @override
+  String localMusicFolderSaveError(Object error) {
+    return 'Tidak dapat menyimpan folder: $error';
+  }
+
+  @override
+  String get localMusicFolderGenericName => 'Folder terpilih';
 }