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/app_id.arb

@@ -904,5 +904,13 @@
   "restaurarCompras": "Pulihkan pembelian",
   "compraError": "Pembelian tidak dapat diselesaikan. Silakan coba lagi.",
   "restauracionSinCompras": "Kami tidak menemukan pembelian sebelumnya di akun ini.",
-  "premiumActivo": "Premium aktif"
+  "premiumActivo": "Premium aktif",
+  "premiumHojaTitulo": "Buka PluriWave Premium",
+  "premiumBeneficioSinAnuncios": "Tanpa iklan di seluruh aplikasi",
+  "premiumBeneficioAndroidAuto": "Android Auto",
+  "premiumBeneficioGrabacion": "Perekaman stasiun",
+  "premiumBeneficioVacaciones": "Rentang liburan untuk alarm",
+  "premiumBeneficioAlarmasIlimitadas": "Alarm tanpa batas (paket gratis mengizinkan hingga 5)",
+  "premiumPagoUnico": "Pembelian sekali bayar, untuk selamanya. Bukan langganan.",
+  "premiumAhoraNo": "Nanti saja"
 }