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_fr.arb

@@ -904,5 +904,13 @@
   "restaurarCompras": "Restaurer les achats",
   "compraError": "Impossible de finaliser l'achat. Veuillez réessayer.",
   "restauracionSinCompras": "Nous n'avons trouvé aucun achat antérieur sur ce compte.",
-  "premiumActivo": "Premium actif"
+  "premiumActivo": "Premium actif",
+  "premiumHojaTitulo": "Débloquer PluriWave Premium",
+  "premiumBeneficioSinAnuncios": "Aucune publicité dans toute l'application",
+  "premiumBeneficioAndroidAuto": "Android Auto",
+  "premiumBeneficioGrabacion": "Enregistrement des stations",
+  "premiumBeneficioVacaciones": "Périodes de vacances pour les alarmes",
+  "premiumBeneficioAlarmasIlimitadas": "Alarmes illimitées (la version gratuite en autorise jusqu'à 5)",
+  "premiumPagoUnico": "Achat unique, pour toujours. Ce n'est pas un abonnement.",
+  "premiumAhoraNo": "Plus tard"
 }