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_hi.dart

@@ -63,22 +63,22 @@ class AppLocalizationsHi extends AppLocalizations {
     Object minutes,
     Object seconds,
   ) {
-    return '$hours ?? $minutes ?? $seconds ??';
+    return '$hours घंटे $minutes मिनट $seconds सेकंड';
   }
 
   @override
   String durationMinutesSeconds(Object minutes, Object seconds) {
-    return '$minutes ?? $seconds ??';
+    return '$minutes मिनट $seconds सेकंड';
   }
 
   @override
   String durationMinutesOnly(Object minutes) {
-    return '$minutes ??';
+    return '$minutes मिनट';
   }
 
   @override
   String durationSecondsOnly(Object seconds) {
-    return '$seconds ??';
+    return '$seconds सेकंड';
   }
 
   @override
@@ -1303,4 +1303,34 @@ class AppLocalizationsHi extends AppLocalizations {
 
   @override
   String get eqDeviceConnected => 'कनेक्टेड';
+
+  @override
+  String get localMusicSectionTitle => 'स्थानीय संगीत (Android Auto)';
+
+  @override
+  String get localMusicSectionDescription =>
+      'गाड़ी में ऑडियो फ़ाइलें ब्राउज़ और चलाने के लिए इस डिवाइस का एक फ़ोल्डर चुनें।';
+
+  @override
+  String get localMusicFolderNotConfigured => 'कोई फ़ोल्डर चुना नहीं गया';
+
+  @override
+  String get localMusicFolderTitle => 'स्थानीय संगीत फ़ोल्डर';
+
+  @override
+  String get localMusicChoosePath => 'फ़ोल्डर चुनें';
+
+  @override
+  String get localMusicChangePath => 'फ़ोल्डर बदलें';
+
+  @override
+  String get localMusicFolderUpdated => 'स्थानीय संगीत फ़ोल्डर अपडेट हुआ';
+
+  @override
+  String localMusicFolderSaveError(Object error) {
+    return 'फ़ोल्डर सहेजा नहीं जा सका: $error';
+  }
+
+  @override
+  String get localMusicFolderGenericName => 'चयनित फ़ोल्डर';
 }