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_ja.dart

@@ -1812,4 +1812,28 @@ class AppLocalizationsJa extends AppLocalizations {
 
   @override
   String get premiumActivo => 'プレミアム有効';
+
+  @override
+  String get premiumHojaTitulo => 'PluriWave Premiumのロックを解除';
+
+  @override
+  String get premiumBeneficioSinAnuncios => 'アプリ全体で広告なし';
+
+  @override
+  String get premiumBeneficioAndroidAuto => 'Android Auto';
+
+  @override
+  String get premiumBeneficioGrabacion => '放送局の録音';
+
+  @override
+  String get premiumBeneficioVacaciones => 'アラームの休暇期間設定';
+
+  @override
+  String get premiumBeneficioAlarmasIlimitadas => 'アラーム数無制限(無料プランは5個まで)';
+
+  @override
+  String get premiumPagoUnico => '買い切りの一度きりの支払いで永久に使用可能。サブスクリプションではありません。';
+
+  @override
+  String get premiumAhoraNo => '後で';
 }