fix(buscar): rebuild the offline banner with offlineAccent

Audit 13.1 (t4 line 641): the banner rendered wifi_off in
colorScheme.error (red) inside a generic glass card. Rebuilt using
offlineAccent (#E8879A) — a token that existed since Tier 1 with no
consumer — for the tint, border and icon, plus the prototype's title/
detail layout and a restyled Retry chip. New offlineBannerTitle key
translated to all 13 locales.

lib/l10n/gen/app_localizations_it.dart

@@ -772,6 +772,9 @@ class AppLocalizationsIt extends AppLocalizations {
   @override
   String get genresTitle => 'Generi';
 
+  @override
+  String get offlineBannerTitle => 'Nessuna connessione';
+
   @override
   String get retryAction => 'Riprova';