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/helpers/fakes_alarmas.dart

@@ -17,6 +17,24 @@ class FakePuertoAlarmasAndroid implements PuertoAlarmasAndroid {
   final _eventos = StreamController<EventoAlarmaAndroid>.broadcast();
   bool ignoraOptimizacionBateria = true;
   int solicitudesExencionBateria = 0;
+  int aperturasConfiguracionNotificaciones = 0;
+
+  /// Extra diagnostico() fields (fix/alarmas-fiabilidad diagnostics screen).
+  /// Default values mirror the previous hardcoded literals in [diagnostico],
+  /// so every existing test that never sets these keeps seeing the exact
+  /// same snapshot as before.
+  bool puedeProgramarExactas = true;
+  bool notificacionesPermitidas = true;
+  bool puedeUsarPantallaCompleta = true;
+  int alarmasNativasPendientes = 0;
+  String fabricante = 'test';
+  int versionSdk = 35;
+
+  /// Test-only failure switch (diagnostics screen, "intent not resolving"
+  /// coverage): when true, every `abrir*`/`solicitar*` system-screen action
+  /// below reports failure (as a real device does when a ROM lacks that
+  /// settings screen), while still recording the attempt via its counter.
+  bool fallaAccionSistema = false;
 
   /// Test-only failure switch (Design D7): when true, [programar] throws
   /// instead of scheduling, enabling failure-path coverage that the fake
@@ -107,19 +125,25 @@ class FakePuertoAlarmasAndroid implements PuertoAlarmasAndroid {
   @override
   Future<DiagnosticoAlarmasAndroid> diagnostico() async =>
       DiagnosticoAlarmasAndroid(
-        puedeProgramarExactas: true,
-        notificacionesPermitidas: true,
-        puedeUsarPantallaCompleta: true,
+        puedeProgramarExactas: puedeProgramarExactas,
+        notificacionesPermitidas: notificacionesPermitidas,
+        puedeUsarPantallaCompleta: puedeUsarPantallaCompleta,
         ignoraOptimizacionBateria: ignoraOptimizacionBateria,
-        alarmasNativasPendientes: 0,
-        fabricante: 'test',
-        versionSdk: 35,
+        alarmasNativasPendientes: alarmasNativasPendientes,
+        fabricante: fabricante,
+        versionSdk: versionSdk,
       );
 
   @override
   Future<bool> solicitarExencionBateria() async {
     solicitudesExencionBateria++;
-    return true;
+    return !fallaAccionSistema;
+  }
+
+  @override
+  Future<bool> abrirConfiguracionNotificaciones() async {
+    aperturasConfiguracionNotificaciones++;
+    return !fallaAccionSistema;
   }
 
   @override
@@ -133,14 +157,23 @@ class FakePuertoAlarmasAndroid implements PuertoAlarmasAndroid {
   Future<List<EstadoSnoozeNativo>> obtenerEstadoSnoozeNativo() async =>
       List.of(snoozesNativos);
 
+  int solicitudesPermisoAlarmasExactas = 0;
+  int solicitudesPermisoPantallaCompleta = 0;
+
   @override
-  Future<bool> solicitarPermisoAlarmasExactas() async => true;
+  Future<bool> solicitarPermisoAlarmasExactas() async {
+    solicitudesPermisoAlarmasExactas++;
+    return !fallaAccionSistema;
+  }
 
   @override
   Future<bool> solicitarPermisoNotificaciones() async => true;
 
   @override
-  Future<bool> solicitarPermisoPantallaCompleta() async => true;
+  Future<bool> solicitarPermisoPantallaCompleta() async {
+    solicitudesPermisoPantallaCompleta++;
+    return !fallaAccionSistema;
+  }
 
   Future<void> dispose() => _eventos.close();
 }