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_zh.dart

@@ -1797,4 +1797,28 @@ class AppLocalizationsZh extends AppLocalizations {
 
   @override
   String get premiumActivo => '高级版已解锁';
+
+  @override
+  String get premiumHojaTitulo => '解锁 PluriWave Premium';
+
+  @override
+  String get premiumBeneficioSinAnuncios => '全应用无广告';
+
+  @override
+  String get premiumBeneficioAndroidAuto => 'Android Auto';
+
+  @override
+  String get premiumBeneficioGrabacion => '电台录音';
+
+  @override
+  String get premiumBeneficioVacaciones => '闹钟的假期时间段';
+
+  @override
+  String get premiumBeneficioAlarmasIlimitadas => '无限闹钟(免费版最多支持5个)';
+
+  @override
+  String get premiumPagoUnico => '一次性付费,永久使用,不是订阅。';
+
+  @override
+  String get premiumAhoraNo => '以后再说';
 }