feat(alarmas): replace one-line reliability button with full diagnostics screen

Surface all six DiagnosticoAlarmasAndroid fields instead of three: the
battery-optimization exemption and native pending-alarm count were
already collected but silently dropped by the old widget. Each failing
signal now offers a "Fix this" action that opens the right system
settings screen (exact alarms, notifications, full-screen intent,
battery optimization), guarded by SDK level and never crashing when a
ROM lacks that screen. Manufacturers known for aggressive background
killing (Xiaomi/Redmi/POCO, Huawei, Oppo, Vivo, OnePlus, Samsung) get
an honest explanation that Autostart must be enabled manually, since
there is no API to detect or grant it.

Notifications now deep-links straight to
ACTION_APP_NOTIFICATION_SETTINGS via a new openNotificationSettings
native method, instead of reusing the runtime permission popup meant
for first-time alarm creation.

New copy is added to all 13 ARB locales with real per-language
translations (not Spanish copies), verified by the ARB parity and
anti-copy tests plus the corruption scanner.

test/servicios/servicio_alarmas_android_test.dart

@@ -20,10 +20,16 @@ void main() {
               return true;
             case 'requestIgnoreBatteryOptimizations':
               return true;
+            case 'openNotificationSettings':
+              return true;
             case 'getActiveRingingAlarmId':
               return 'ring1';
             case 'stopActiveAlarm':
-              return {'stopped': true, 'wasRinging': true, 'activeAlarmId': 'ring1'};
+              return {
+                'stopped': true,
+                'wasRinging': true,
+                'activeAlarmId': 'ring1',
+              };
           }
           return null;
         });
@@ -111,6 +117,22 @@ void main() {
     },
   );
 
+  test(
+    'abrirConfiguracionNotificaciones invoca openNotificationSettings '
+    '(deep link a Settings, distinto del permiso runtime de la primera vez)',
+    () async {
+      final servicio = ServicioAlarmasAndroid(channel: channel);
+
+      final abierto = await servicio.abrirConfiguracionNotificaciones();
+
+      expect(abierto, isTrue);
+      expect(
+        llamadas.map((c) => c.method),
+        contains('openNotificationSettings'),
+      );
+    },
+  );
+
   test(
     'detenerSonidoActivo mapea el resultado nativo confirmado a ResultadoDetencion',
     () async {
@@ -144,21 +166,15 @@ void main() {
     },
   );
 
-  test(
-    'alarmaSonandoId propaga el error del canal (fail-toward-silence, '
-    'Finding 2)',
-    () async {
-      TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
-          .setMockMethodCallHandler(channel, (call) async {
-            llamadas.add(call);
-            throw PlatformException(code: 'QUERY_FAILED', message: 'boom');
-          });
-      final servicio = ServicioAlarmasAndroid(channel: channel);
+  test('alarmaSonandoId propaga el error del canal (fail-toward-silence, '
+      'Finding 2)', () async {
+    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
+        .setMockMethodCallHandler(channel, (call) async {
+          llamadas.add(call);
+          throw PlatformException(code: 'QUERY_FAILED', message: 'boom');
+        });
+    final servicio = ServicioAlarmasAndroid(channel: channel);
 
-      expect(
-        () => servicio.alarmaSonandoId(),
-        throwsA(isA<PlatformException>()),
-      );
-    },
-  );
+    expect(() => servicio.alarmaSonandoId(), throwsA(isA<PlatformException>()));
+  });
 }