i18n(alarm): localize all native notification, channel and chooser texts

Centralize every native-side user-facing string in a single
AlarmNotificationStrings store written by Flutter via a new
setNotificationStrings MethodChannel whenever the app locale changes,
and read at notification/channel build time (with English fallbacks)
even when the engine is dead. This replaces the hardcoded Spanish text
in the ringing notification ("Alarma PluriWave", "Posponer", "Detener"),
the pre-notice notification ("Posponer", "Omitir esta vez"), both
notification channels (names + descriptions) and the file-action
choosers ("Abrir carpeta", "Abrir grabación").

The per-alarm preNoticeTemplate/snoozeCountdown template+label args are
dropped from scheduleAlarm and the persisted spec and folded into the
shared store, so a locale change now also relocalizes already-scheduled
alarms. Channels are re-created on each use so their name/description
refresh after a language switch.

Adds alarmRingingNotificationTitle, alarmFire/PreNoticeChannelName,
alarmFire/PreNoticeChannelDescription and openFolder/openRecording
chooser keys across all 13 locales (reusing snoozeAction, stopAlarmAction,
skipNextAction, snoozeAgainAction). Rewrites the template test around
setNotificationStrings. Kotlin is static-reviewed only; no Android build
environment available here.

lib/servicios/servicio_alarmas_android.dart

@@ -172,29 +172,41 @@ class ServicioAlarmasAndroid implements PuertoAlarmasAndroid {
   @override
   void configurarLocalizaciones(AppLocalizations l10n) {
     _l10n = l10n;
+    // Push every localized notification/channel/chooser string to the native
+    // side so it can build localized notifications even when the Flutter engine
+    // is dead (alarm fired from a killed app). Fire-and-forget; runs once per
+    // locale change (callers guard against per-rebuild churn).
+    unawaited(_enviarTextosNotificacion(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}',
-    );
+  Future<void> _enviarTextosNotificacion(AppLocalizations l10n) async {
+    try {
+      await _channel.invokeMethod<void>('setNotificationStrings', {
+        'ringTitle': l10n.alarmRingingNotificationTitle,
+        'snoozeLabel': l10n.snoozeAction,
+        'stopLabel': l10n.stopAlarmAction,
+        'skipLabel': l10n.skipNextAction,
+        'snoozeAgainLabel': l10n.snoozeAgainAction,
+        'fireChannelName': l10n.alarmFireChannelName,
+        'fireChannelDescription': l10n.alarmFireChannelDescription,
+        'preNoticeChannelName': l10n.alarmPreNoticeChannelName,
+        'preNoticeChannelDescription': l10n.alarmPreNoticeChannelDescription,
+        'preNoticeTemplate': _plantillaMinutos(l10n.preNoticeCountdown),
+        'snoozeCountdownTemplate': _plantillaMinutos(l10n.snoozeCountdown),
+        'openFolderTitle': l10n.openFolderChooserTitle,
+        'openRecordingTitle': l10n.openRecordingChooserTitle,
+      });
+    } catch (e) {
+      debugPrint('[PluriWave][alarmas] setNotificationStrings ERROR $e');
+    }
   }
 
-  /// Same sentinel strategy as [_preNoticeTemplate], but for the snooze
-  /// countdown notification re-posted every minute while an alarm is snoozed.
-  static String _snoozeCountdownTemplate(AppLocalizations l10n) {
+  /// Turns a localized `{int} -> String` message into a template with a literal
+  /// `{minutes}` placeholder for Kotlin to fill at fire time: it calls the
+  /// message with a unique sentinel and swaps the sentinel back for `{minutes}`.
+  static String _plantillaMinutos(String Function(int) traducir) {
     const sentinel = 42424242;
-    return l10n.snoozeCountdown(sentinel).replaceFirst(
-      sentinel.toString(),
-      '{minutes}',
-    );
+    return traducir(sentinel).replaceFirst(sentinel.toString(), '{minutes}');
   }
 
   @override
@@ -216,10 +228,6 @@ class ServicioAlarmasAndroid implements PuertoAlarmasAndroid {
     final programada = await _channel.invokeMethod<bool>('scheduleAlarm', {
       'id': alarma.id,
       'title': localizedAlarmName(_textos, alarma.nombre),
-      'preNoticeTemplate': _preNoticeTemplate(_textos),
-      'snoozeCountdownTemplate': _snoozeCountdownTemplate(_textos),
-      'snoozeAgainLabel': _textos.snoozeAgainAction,
-      'snoozeStopLabel': _textos.stopAlarmAction,
       'triggerAtMillis': proxima.millisecondsSinceEpoch,
       'preNoticeAtMillis':
           alarma.snoozeHasta == null