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.

test/servicios/servicio_dispositivo_audio_real_test.dart

@@ -146,5 +146,61 @@ void main() {
         expect(granted, isFalse);
       },
     );
+
+    // ── Fix: robust active-device detection (stale green dot) ────────────────
+
+    test(
+      'resubscribir sends cancel+listen to the event channel and forwards '
+      'the device the fresh onListen emits',
+      () async {
+        var listens = 0;
+        var cancels = 0;
+        TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
+            .setMockStreamHandler(
+              const EventChannel(methodChannelName),
+              MockStreamHandler.inline(
+                onListen: (arguments, events) {
+                  listens++;
+                  // Mirrors the native onListen immediate resync: every
+                  // (re)subscription receives the current active device.
+                  events.success({
+                    'id': 'bt_a2dp:AA:BB:CC:DD:EE:FF',
+                    'type': 8,
+                    'name': 'My BT Device',
+                  });
+                },
+                onCancel: (arguments) => cancels++,
+              ),
+            );
+        addTearDown(() {
+          TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
+              .setMockStreamHandler(
+                const EventChannel(methodChannelName),
+                null,
+              );
+        });
+
+        final servicioLocal = ServicioDispositivoAudioReal();
+        addTearDown(servicioLocal.dispose);
+
+        // The constructor's initial subscription delivers the first resync.
+        final primero = await servicioLocal.onDispositivoCambiado.first;
+        expect(primero.id, 'bt_a2dp:AA:BB:CC:DD:EE:FF');
+        expect(listens, 1);
+        expect(cancels, 0);
+
+        final segundoFuturo = servicioLocal.onDispositivoCambiado.first;
+        await servicioLocal.resubscribir();
+        final segundo = await segundoFuturo;
+
+        expect(cancels, 1);
+        expect(listens, 2);
+        expect(segundo.tipo, TipoDispositivo.bluetoothA2dp);
+        expect(
+          servicioLocal.dispositivoActual?.id,
+          'bt_a2dp:AA:BB:CC:DD:EE:FF',
+        );
+      },
+    );
   });
 }