fix(paywall): add dismiss controls and honest premium copy

The premium sheet had no close affordance or way to defer, and its
copy only said "Función Premium" without stating what it unlocks.
Adds a header close (X) button and a "not now" secondary action so
dismissal is never harder than purchasing, and replaces the bare
title with a concrete, honest breakdown of the 5 things premium
unlocks (no ads, Android Auto, station recording, alarm vacation
ranges, unlimited alarms) plus the one-time-purchase framing. The
phone equalizer is never listed, since it stays free for everyone.
New l10n keys added to all 13 locales.

lib/l10n/gen/app_localizations_ar.dart

@@ -1863,4 +1863,29 @@ class AppLocalizationsAr extends AppLocalizations {
 
   @override
   String get premiumActivo => 'النسخة المميزة مفعّلة';
+
+  @override
+  String get premiumHojaTitulo => 'افتح PluriWave Premium';
+
+  @override
+  String get premiumBeneficioSinAnuncios => 'بدون إعلانات في التطبيق بالكامل';
+
+  @override
+  String get premiumBeneficioAndroidAuto => 'Android Auto';
+
+  @override
+  String get premiumBeneficioGrabacion => 'تسجيل المحطات';
+
+  @override
+  String get premiumBeneficioVacaciones => 'فترات إجازة للمنبهات';
+
+  @override
+  String get premiumBeneficioAlarmasIlimitadas =>
+      'منبهات غير محدودة (تسمح الخطة المجانية بحتى 5)';
+
+  @override
+  String get premiumPagoUnico => 'دفعة واحدة، للأبد. ليس اشتراكًا.';
+
+  @override
+  String get premiumAhoraNo => 'ليس الآن';
 }