feat(alarm): add musical alarm foundation

lib/servicios/servicio_alarmas_android.dart

@@ -0,0 +1,59 @@
+import 'package:flutter/services.dart';
+
+import '../modelos/alarma_musical.dart';
+
+class DiagnosticoAlarmasAndroid {
+  const DiagnosticoAlarmasAndroid({
+    required this.puedeProgramarExactas,
+    required this.notificacionesPermitidas,
+    required this.fabricante,
+    required this.versionSdk,
+  });
+
+  final bool puedeProgramarExactas;
+  final bool notificacionesPermitidas;
+  final String fabricante;
+  final int versionSdk;
+
+  factory DiagnosticoAlarmasAndroid.fromMap(Map<Object?, Object?> map) {
+    return DiagnosticoAlarmasAndroid(
+      puedeProgramarExactas: map['canScheduleExactAlarms'] as bool? ?? true,
+      notificacionesPermitidas: map['notificationsEnabled'] as bool? ?? true,
+      fabricante: map['manufacturer'] as String? ?? 'Android',
+      versionSdk: map['sdkInt'] as int? ?? 0,
+    );
+  }
+}
+
+class ServicioAlarmasAndroid {
+  ServicioAlarmasAndroid({
+    MethodChannel channel = const MethodChannel('pluriwave/alarm_scheduler'),
+  }) : _channel = channel;
+
+  final MethodChannel _channel;
+
+  Future<void> programar(AlarmaMusical alarma) async {
+    final proxima = alarma.proximaEjecucion;
+    if (proxima == null || !alarma.activa) {
+      await cancelar(alarma.id);
+      return;
+    }
+    await _channel.invokeMethod<void>('scheduleAlarm', {
+      'id': alarma.id,
+      'title': alarma.nombre,
+      'triggerAtMillis': proxima.millisecondsSinceEpoch,
+      'preNoticeAtMillis':
+          proxima.subtract(const Duration(minutes: 30)).millisecondsSinceEpoch,
+    });
+  }
+
+  Future<void> cancelar(String alarmaId) =>
+      _channel.invokeMethod<void>('cancelAlarm', {'id': alarmaId});
+
+  Future<DiagnosticoAlarmasAndroid> diagnostico() async {
+    final raw = await _channel.invokeMethod<Map<Object?, Object?>>(
+      'diagnostics',
+    );
+    return DiagnosticoAlarmasAndroid.fromMap(raw ?? const {});
+  }
+}