fix(alarms): prevent overlapping playback

lib/app.dart

@@ -63,6 +63,8 @@ class _PaginaPrincipalState extends State<_PaginaPrincipal> {
   StreamSubscription<AlarmaMusical>? _alarmaVencidaSubscription;
   EstadoRadio? _estadoSuscrito;
   bool _alarmaInicialProcesada = false;
+  bool _alarmaSonandoActiva = false;
+  String? _alarmaSonandoId;
 
   static const _paginas = [
     PantallaInicio(),
@@ -224,21 +226,58 @@ class _PaginaPrincipalState extends State<_PaginaPrincipal> {
       setState(() => _indice = 3);
       return;
     }
-    await Navigator.of(context).push(
-      MaterialPageRoute<void>(
-        builder: (_) => PantallaAlarmaSonando(alarma: alarma!),
-        fullscreenDialog: true,
-      ),
-    );
+    await _mostrarAlarmaSonando(alarma);
   }
 
   Future<void> _abrirAlarmaDirecta(AlarmaMusical alarma) async {
-    await Navigator.of(context).push(
-      MaterialPageRoute<void>(
-        builder: (_) => PantallaAlarmaSonando(alarma: alarma),
-        fullscreenDialog: true,
-      ),
+    await _mostrarAlarmaSonando(alarma);
+  }
+
+  Future<void> _mostrarAlarmaSonando(AlarmaMusical alarma) async {
+    final alarmas = context.read<EstadoAlarmas>();
+    alarmas.marcarEjecucionGestionada(alarma);
+
+    if (_alarmaSonandoActiva) {
+      debugPrint(
+        '[PluriWave][alarmas] alarma ignorada porque ya hay una activa id=${alarma.id} activa=$_alarmaSonandoId',
+      );
+      await alarmas.android.ocultarNotificacionAlarma(alarma.id);
+      return;
+    }
+
+    _alarmaSonandoActiva = true;
+    _alarmaSonandoId = alarma.id;
+
+    try {
+      await _prearrancarAudioAlarma(alarma);
+      if (!mounted) return;
+      await Navigator.of(context).push(
+        MaterialPageRoute<void>(
+          builder:
+              (_) => PantallaAlarmaSonando(
+                alarma: alarma,
+                audioPrearrancado: alarma.emisora != null,
+              ),
+          fullscreenDialog: true,
+        ),
+      );
+    } finally {
+      if (_alarmaSonandoId == alarma.id) {
+        _alarmaSonandoActiva = false;
+        _alarmaSonandoId = null;
+      }
+    }
+  }
+
+  Future<void> _prearrancarAudioAlarma(AlarmaMusical alarma) async {
+    final emisora = alarma.emisora;
+    if (emisora == null) return;
+    final radio = context.read<EstadoRadio>();
+    debugPrint(
+      '[PluriWave][alarmas] prearrancar emisora alarma id=${alarma.id} emisora=${emisora.nombre}',
     );
+    await radio.audio.setVolumen(alarma.volumen.clamp(0.0, 1.0));
+    unawaited(radio.reproducir(emisora));
   }
 
   void _mostrarTimerDialog(BuildContext context) {

lib/estado/estado_alarmas.dart

@@ -96,6 +96,16 @@ class EstadoAlarmas extends ChangeNotifier {
     notifyListeners();
   }
 
+  void marcarEjecucionGestionada(AlarmaMusical alarma) {
+    final proxima = alarma.proximaEjecucion;
+    if (proxima == null) return;
+    final key = '${alarma.id}:${proxima.millisecondsSinceEpoch}';
+    _ejecucionesEmitidas.add(key);
+    debugPrint(
+      '[PluriWave][alarmas] ejecucion gestionada id=${alarma.id} proxima=${proxima.toIso8601String()}',
+    );
+  }
+
   Future<void> eliminarAlarma(String id) async {
     debugPrint('[PluriWave][alarmas] eliminar id=$id');
     final config = await servicio.eliminarAlarma(id);

lib/pantallas/pantalla_alarma_sonando.dart

@@ -11,9 +11,14 @@ import '../servicios/servicio_audio.dart';
 import '../widgets/pluri_glass_surface.dart';
 
 class PantallaAlarmaSonando extends StatefulWidget {
-  const PantallaAlarmaSonando({super.key, required this.alarma});
+  const PantallaAlarmaSonando({
+    super.key,
+    required this.alarma,
+    this.audioPrearrancado = false,
+  });
 
   final AlarmaMusical alarma;
+  final bool audioPrearrancado;
 
   @override
   State<PantallaAlarmaSonando> createState() => _PantallaAlarmaSonandoState();
@@ -45,7 +50,9 @@ class _PantallaAlarmaSonandoState extends State<PantallaAlarmaSonando> {
 
     _radioIntentada = true;
     await radio.audio.setVolumen(widget.alarma.volumen.clamp(0.0, 1.0));
-    unawaited(radio.reproducir(emisora));
+    if (!widget.audioPrearrancado) {
+      unawaited(radio.reproducir(emisora));
+    }
 
     _estadoSub = radio.estadoStream.listen((estado) {
       if (estado == EstadoReproduccion.reproduciendo && mounted) {
@@ -59,6 +66,9 @@ class _PantallaAlarmaSonandoState extends State<PantallaAlarmaSonando> {
     _fallbackTimer = Timer(const Duration(seconds: 12), () {
       if (mounted) _iniciarFallback();
     });
+    if (widget.audioPrearrancado && radio.audio.estaSonando) {
+      _fallbackTimer?.cancel();
+    }
   }
 
   Future<void> _iniciarFallback() async {