feat(alarms): native reliability fixes and end-to-end snooze

- Use mediaPlayback|systemExempted FGS type with FOREGROUND_SERVICE_SYSTEM_EXEMPTED so alarms fire on Android 14+ (FOREGROUND_SERVICE_ALARM does not exist in the SDK)
- Deduplicate fire notifications: the foreground service FSI notification is the single owner; receiver path removed
- Notification channel v2 with alarm sound URI and USAGE_ALARM attributes, one-time guarded migration from legacy channels
- Pass fallback station through the MethodChannel (NativeAlarmSpec schemaVersion 3) with a three-stage audio chain: primary -> fallback station -> bundled WAV
- Native fade-in volume ramp honoring fadeInSegundos when the app is killed
- Request battery-optimization exemption once, tracked with a persisted asked-once flag
- Fix snooze end-to-end: native ACTION_SNOOZE now reports back to Flutter (snoozed event + cold-start sync), snooze anchor unified to occurrence+minutes on both sides, periodic recalc no longer erases an active snooze
- Add snooze buttons (3/5/10/custom) to the ringing screen with shared audio teardown
- Redesign ringing screen on PluriWaveScaffold with reduced-motion-aware entry animation (new PluriAnimate helper)
- Alarm editor: live next-trigger preview, searchable station pickers (primary and fallback), configurable snooze duration, volume floor down to 0
- New alarm strings localized across all 13 locales
- New unit/widget tests for the snooze flow, alarm bridge payloads, ringing screen and editor (77 tests green)
- SDD artifacts for the app-quality-and-native-alarms change (explore, proposal, spec, design, tasks, apply progress)

lib/servicios/servicio_alarmas_android.dart

@@ -16,14 +16,20 @@ class EventoAlarmaAndroid {
     this.triggerAtMillis = 0,
     this.occurrenceAtMillis = 0,
     this.snoozeMinutes = 5,
+    this.snoozeUntilMillis = 0,
   });
 
+  /// Action reported when the native service snoozed an alarm by itself
+  /// (notification "Posponer" while the app may be backgrounded/killed).
+  static const accionSnoozed = 'snoozed';
+
   final String alarmaId;
   final String titulo;
   final String accion;
   final int triggerAtMillis;
   final int occurrenceAtMillis;
   final int snoozeMinutes;
+  final int snoozeUntilMillis;
 
   factory EventoAlarmaAndroid.fromMap(Map<Object?, Object?> map) {
     return EventoAlarmaAndroid(
@@ -33,6 +39,34 @@ class EventoAlarmaAndroid {
       triggerAtMillis: (map['triggerAtMillis'] as num?)?.toInt() ?? 0,
       occurrenceAtMillis: (map['occurrenceAtMillis'] as num?)?.toInt() ?? 0,
       snoozeMinutes: (map['snoozeMinutes'] as num?)?.toInt() ?? 5,
+      snoozeUntilMillis: (map['snoozeUntilMillis'] as num?)?.toInt() ?? 0,
+    );
+  }
+}
+
+/// Active native snooze persisted by `AlarmScheduler` (Kotlin). Used on cold
+/// start so Flutter (single source of truth) can import snoozes performed
+/// while the engine was dead.
+class EstadoSnoozeNativo {
+  const EstadoSnoozeNativo({
+    required this.alarmaId,
+    required this.snoozeHasta,
+    required this.snoozeOrigen,
+  });
+
+  final String alarmaId;
+  final DateTime snoozeHasta;
+  final DateTime snoozeOrigen;
+
+  factory EstadoSnoozeNativo.fromMap(Map<Object?, Object?> map) {
+    return EstadoSnoozeNativo(
+      alarmaId: map['alarmId'] as String? ?? '',
+      snoozeHasta: DateTime.fromMillisecondsSinceEpoch(
+        (map['snoozeUntilMillis'] as num?)?.toInt() ?? 0,
+      ),
+      snoozeOrigen: DateTime.fromMillisecondsSinceEpoch(
+        (map['snoozeOriginMillis'] as num?)?.toInt() ?? 0,
+      ),
     );
   }
 }
@@ -60,8 +94,7 @@ class DiagnosticoAlarmasAndroid {
     return DiagnosticoAlarmasAndroid(
       puedeProgramarExactas: map['canScheduleExactAlarms'] as bool? ?? true,
       notificacionesPermitidas: map['notificationsEnabled'] as bool? ?? true,
-      puedeUsarPantallaCompleta:
-          map['canUseFullScreenIntent'] as bool? ?? true,
+      puedeUsarPantallaCompleta: map['canUseFullScreenIntent'] as bool? ?? true,
       ignoraOptimizacionBateria:
           map['isIgnoringBatteryOptimizations'] as bool? ?? true,
       alarmasNativasPendientes: map['nativePendingAlarmsCount'] as int? ?? 0,
@@ -100,10 +133,12 @@ abstract class PuertoAlarmasAndroid {
   Future<bool> solicitarPermisoAlarmasExactas();
   Future<bool> solicitarPermisoNotificaciones();
   Future<bool> solicitarPermisoPantallaCompleta();
+  Future<bool> solicitarExencionBateria();
   Future<void> confirmarAudioFlutter(String alarmaId);
   Future<DiagnosticoAlarmasAndroid> diagnostico();
   Future<EventoAlarmaAndroid?> obtenerEventoInicial();
   Future<List<EjecucionAlarmaNativa>> obtenerEjecucionesNativasGestionadas();
+  Future<List<EstadoSnoozeNativo>> obtenerEstadoSnoozeNativo();
 }
 
 class ServicioAlarmasAndroid implements PuertoAlarmasAndroid {
@@ -151,7 +186,9 @@ class ServicioAlarmasAndroid implements PuertoAlarmasAndroid {
       'triggerAtMillis': proxima.millisecondsSinceEpoch,
       'preNoticeAtMillis':
           alarma.snoozeHasta == null
-              ? proxima.subtract(const Duration(minutes: 30)).millisecondsSinceEpoch
+              ? proxima
+                  .subtract(const Duration(minutes: 30))
+                  .millisecondsSinceEpoch
               : 0,
       'hour': alarma.hora,
       'minute': alarma.minuto,
@@ -169,8 +206,14 @@ class ServicioAlarmasAndroid implements PuertoAlarmasAndroid {
               ? null
               : localizedStationName(_textos, alarma.emisora!.nombre),
       'stationUrl': alarma.emisora?.url,
+      'fallbackStationName':
+          alarma.emisoraFallback == null
+              ? null
+              : localizedStationName(_textos, alarma.emisoraFallback!.nombre),
+      'fallbackStationUrl': alarma.emisoraFallback?.url,
       'fallbackSound': alarma.sonidoInterno.name,
       'volume': alarma.volumen,
+      'fadeInSegundos': alarma.fadeInSegundos,
     });
     if (programada != true) {
       throw StateError(_textos.androidExactAlarmScheduleError);
@@ -217,6 +260,14 @@ class ServicioAlarmasAndroid implements PuertoAlarmasAndroid {
     return abierto ?? false;
   }
 
+  @override
+  Future<bool> solicitarExencionBateria() async {
+    final abierto = await _channel.invokeMethod<bool>(
+      'requestIgnoreBatteryOptimizations',
+    );
+    return abierto ?? false;
+  }
+
   @override
   Future<DiagnosticoAlarmasAndroid> diagnostico() async {
     debugPrint('[PluriWave][alarmas] diagnostico android');
@@ -261,6 +312,23 @@ class ServicioAlarmasAndroid implements PuertoAlarmasAndroid {
         .toList();
   }
 
+  @override
+  Future<List<EstadoSnoozeNativo>> obtenerEstadoSnoozeNativo() async {
+    final raw = await _channel.invokeMethod<List<Object?>>(
+      'getNativeSnoozeState',
+    );
+    if (raw == null || raw.isEmpty) return const [];
+    return raw
+        .whereType<Map<Object?, Object?>>()
+        .map(EstadoSnoozeNativo.fromMap)
+        .where(
+          (estado) =>
+              estado.alarmaId.isNotEmpty &&
+              estado.snoozeHasta.millisecondsSinceEpoch > 0,
+        )
+        .toList();
+  }
+
   Future<void> _logAndInvokeVoid(String method, Map<String, Object?> args) {
     debugPrint('[PluriWave][alarmas] $method $args');
     return _channel.invokeMethod<void>(method, args);