feat(iap): add freemium unlock via one-time in-app purchase

Adds a permanent, non-consumable premium unlock (EstadoEntitlement +
PuertoCompras/ServicioComprasPlayBilling) that removes ads and unlocks
alarm vacations, alarms past a 5-alarm free cap, recording start, and
full Android Auto browsing. The phone equalizer stays free for everyone.

- Entitlement is prefs-backed (compra_premium_v1), fail-open, and
  resolvable headlessly via esPremiumPersistido() for the Android Auto
  audio handler, which registers before runApp.
- Android Auto reduced mode keeps the real root folder labels for free
  users; browsing into any of them (and playFromMediaId/playFromSearch/
  skipToNext/skipToPrevious) is blocked at the getChildren/servicio_audio
  choke points, with a locked "Función Premium" item as the backstop.
  Current-station play/pause/stop stays untouched. A free -> premium
  transition actively invalidates the head unit's cached browse tree.
- Ads (top banner + capped interstitial before adding a station or an
  alarm) are gated behind entitlement via ServicioAnuncios, using
  official Google test ad unit IDs pending AdMob provisioning.
- Alarm cap UX shows an explanatory message with a secondary unlock
  action rather than a bare paywall jump; existing data is grandfathered.
- 4 new localization keys translated across all 13 supported locales.

Co-located tests use strict TDD (RED test before implementation) for
every new pure-logic unit; full existing suite passes unchanged.

lib/l10n/gen/app_localizations.dart

@@ -3325,6 +3325,30 @@ abstract class AppLocalizations {
   /// In es, this message translates to:
   /// **'Desactivar'**
   String get autoEqDisableOption;
+
+  /// No description provided for @funcionPremium.
+  ///
+  /// In es, this message translates to:
+  /// **'Función Premium'**
+  String get funcionPremium;
+
+  /// No description provided for @limiteAlarmasAlcanzado.
+  ///
+  /// In es, this message translates to:
+  /// **'Has alcanzado el límite de 5 alarmas gratuitas.'**
+  String get limiteAlarmasAlcanzado;
+
+  /// No description provided for @desbloquearPremium.
+  ///
+  /// In es, this message translates to:
+  /// **'Desbloquear Premium'**
+  String get desbloquearPremium;
+
+  /// No description provided for @restaurarCompras.
+  ///
+  /// In es, this message translates to:
+  /// **'Restaurar compras'**
+  String get restaurarCompras;
 }
 
 class _AppLocalizationsDelegate

lib/l10n/gen/app_localizations_ar.dart

@@ -1840,4 +1840,17 @@ class AppLocalizationsAr extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'تعطيل';
+
+  @override
+  String get funcionPremium => 'ميزة مميزة';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'لقد وصلت إلى الحد المجاني وهو 5 منبهات.';
+
+  @override
+  String get desbloquearPremium => 'فتح النسخة المميزة';
+
+  @override
+  String get restaurarCompras => 'استعادة المشتريات';
 }

lib/l10n/gen/app_localizations_bn.dart

@@ -1851,4 +1851,17 @@ class AppLocalizationsBn extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'বন্ধ করুন';
+
+  @override
+  String get funcionPremium => 'প্রিমিয়াম বৈশিষ্ট্য';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'আপনি বিনামূল্যে ৫টি অ্যালার্মের সীমায় পৌঁছেছেন।';
+
+  @override
+  String get desbloquearPremium => 'প্রিমিয়াম আনলক করুন';
+
+  @override
+  String get restaurarCompras => 'কেনাকাটা পুনরুদ্ধার করুন';
 }

lib/l10n/gen/app_localizations_de.dart

@@ -1864,4 +1864,17 @@ class AppLocalizationsDe extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'Deaktivieren';
+
+  @override
+  String get funcionPremium => 'Premium-Funktion';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'Du hast das kostenlose Limit von 5 Weckern erreicht.';
+
+  @override
+  String get desbloquearPremium => 'Premium freischalten';
+
+  @override
+  String get restaurarCompras => 'Käufe wiederherstellen';
 }

lib/l10n/gen/app_localizations_en.dart

@@ -1843,4 +1843,17 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'Disable';
+
+  @override
+  String get funcionPremium => 'Premium Feature';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'You\'ve reached the free 5-alarm limit.';
+
+  @override
+  String get desbloquearPremium => 'Unlock Premium';
+
+  @override
+  String get restaurarCompras => 'Restore purchases';
 }

lib/l10n/gen/app_localizations_es.dart

@@ -1857,4 +1857,17 @@ class AppLocalizationsEs extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'Desactivar';
+
+  @override
+  String get funcionPremium => 'Función Premium';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'Has alcanzado el límite de 5 alarmas gratuitas.';
+
+  @override
+  String get desbloquearPremium => 'Desbloquear Premium';
+
+  @override
+  String get restaurarCompras => 'Restaurar compras';
 }

lib/l10n/gen/app_localizations_fr.dart

@@ -1870,4 +1870,17 @@ class AppLocalizationsFr extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'Désactiver';
+
+  @override
+  String get funcionPremium => 'Fonctionnalité Premium';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'Vous avez atteint la limite gratuite de 5 alarmes.';
+
+  @override
+  String get desbloquearPremium => 'Débloquer Premium';
+
+  @override
+  String get restaurarCompras => 'Restaurer les achats';
 }

lib/l10n/gen/app_localizations_hi.dart

@@ -1844,4 +1844,17 @@ class AppLocalizationsHi extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'बंद करें';
+
+  @override
+  String get funcionPremium => 'प्रीमियम सुविधा';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'आप मुफ़्त 5 अलार्म की सीमा तक पहुँच गए हैं।';
+
+  @override
+  String get desbloquearPremium => 'प्रीमियम अनलॉक करें';
+
+  @override
+  String get restaurarCompras => 'खरीदारी पुनर्स्थापित करें';
 }

lib/l10n/gen/app_localizations_id.dart

@@ -1854,4 +1854,17 @@ class AppLocalizationsId extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'Nonaktifkan';
+
+  @override
+  String get funcionPremium => 'Fitur Premium';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'Anda telah mencapai batas gratis 5 alarm.';
+
+  @override
+  String get desbloquearPremium => 'Buka Premium';
+
+  @override
+  String get restaurarCompras => 'Pulihkan pembelian';
 }

lib/l10n/gen/app_localizations_it.dart

@@ -1867,4 +1867,17 @@ class AppLocalizationsIt extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'Disattiva';
+
+  @override
+  String get funcionPremium => 'Funzione Premium';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'Hai raggiunto il limite gratuito di 5 sveglie.';
+
+  @override
+  String get desbloquearPremium => 'Sblocca Premium';
+
+  @override
+  String get restaurarCompras => 'Ripristina acquisti';
 }

lib/l10n/gen/app_localizations_ja.dart

@@ -1791,4 +1791,16 @@ class AppLocalizationsJa extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => '無効化';
+
+  @override
+  String get funcionPremium => 'プレミアム機能';
+
+  @override
+  String get limiteAlarmasAlcanzado => '無料プランのアラーム上限（5件）に達しました。';
+
+  @override
+  String get desbloquearPremium => 'プレミアムを解除';
+
+  @override
+  String get restaurarCompras => '購入を復元';
 }

lib/l10n/gen/app_localizations_pt.dart

@@ -1854,4 +1854,17 @@ class AppLocalizationsPt extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'Desativar';
+
+  @override
+  String get funcionPremium => 'Recurso Premium';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'Você atingiu o limite gratuito de 5 alarmes.';
+
+  @override
+  String get desbloquearPremium => 'Desbloquear Premium';
+
+  @override
+  String get restaurarCompras => 'Restaurar compras';
 }

lib/l10n/gen/app_localizations_ru.dart

@@ -1861,4 +1861,17 @@ class AppLocalizationsRu extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => 'Отключить';
+
+  @override
+  String get funcionPremium => 'Премиум-функция';
+
+  @override
+  String get limiteAlarmasAlcanzado =>
+      'Вы достигли бесплатного лимита в 5 будильников.';
+
+  @override
+  String get desbloquearPremium => 'Разблокировать Премиум';
+
+  @override
+  String get restaurarCompras => 'Восстановить покупки';
 }

lib/l10n/gen/app_localizations_zh.dart

@@ -1776,4 +1776,16 @@ class AppLocalizationsZh extends AppLocalizations {
 
   @override
   String get autoEqDisableOption => '关闭';
+
+  @override
+  String get funcionPremium => '高级功能';
+
+  @override
+  String get limiteAlarmasAlcanzado => '您已达到免费版 5 个闹钟的上限。';
+
+  @override
+  String get desbloquearPremium => '解锁高级版';
+
+  @override
+  String get restaurarCompras => '恢复购买';
 }