fix(alarm): localize pre-notice countdown and fix snooze dismiss

Replace hardcoded Spanish pre-notice text with computed remaining
minutes using l10n template passed via MethodChannel. Fix snooze
dismiss in dead-app state with canPop guard and SystemNavigator.pop
fallback.

lib/servicios/servicio_alarmas_android.dart

@@ -170,6 +170,19 @@ class ServicioAlarmasAndroid implements PuertoAlarmasAndroid {
     _l10n = l10n;
   }
 
+  /// Builds a pre-notice template string with a literal `{minutes}` placeholder
+  /// for Kotlin to replace at broadcast-receiver fire time.
+  ///
+  /// Strategy: call [preNoticeCountdown] with a unique sentinel integer and
+  /// replace the sentinel's string representation with `{minutes}`.
+  static String _preNoticeTemplate(AppLocalizations l10n) {
+    const sentinel = 42424242;
+    return l10n.preNoticeCountdown(sentinel).replaceFirst(
+      sentinel.toString(),
+      '{minutes}',
+    );
+  }
+
   @override
   Stream<EventoAlarmaAndroid> get eventosAlarma => _eventosController.stream;
 
@@ -189,6 +202,7 @@ class ServicioAlarmasAndroid implements PuertoAlarmasAndroid {
     final programada = await _channel.invokeMethod<bool>('scheduleAlarm', {
       'id': alarma.id,
       'title': localizedAlarmName(_textos, alarma.nombre),
+      'preNoticeTemplate': _preNoticeTemplate(_textos),
       'triggerAtMillis': proxima.millisecondsSinceEpoch,
       'preNoticeAtMillis':
           alarma.snoozeHasta == null