Completa i18n IT/EN/FR/DE/ES su sito pubblico, area autenticata e admin.

Tutte le view marketing, legali, viewer, dashboard e admin usano t(); mailer utente-facing e flash localizzati; admin con LocaleResolver e selettore lingua.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/controllers/admin/base_controller.rb

@@ -3,20 +3,40 @@ module Admin
     layout "admin"
     protect_from_forgery with: :exception
 
+    before_action :set_admin_locale
     before_action :require_admin_login
 
     include ::AdminHelper
     helper ApplicationHelper
     helper RecordingsArchiveHelper
-    helper_method :current_admin_account, :admin_logged_in?
+    helper_method :current_admin_account, :admin_logged_in?, :current_locale, :language_options, :current_language_option
 
     private
 
+    def set_admin_locale
+      I18n.locale = LocaleResolver.resolve(
+        cookie_jar: request.cookie_jar,
+        accept_language: request.get_header("HTTP_ACCEPT_LANGUAGE")
+      )
+    end
+
+    def current_locale
+      I18n.locale
+    end
+
+    def language_options
+      LocaleResolver.language_options
+    end
+
+    def current_language_option
+      LocaleResolver.current_language_option
+    end
+
     def require_admin_login
       return if admin_logged_in?
 
       session[:admin_return_to] = request.fullpath unless request.path == admin_login_path
-      redirect_to admin_login_path, alert: "Accedi per continuare"
+      redirect_to admin_login_path, alert: t("admin.flash.login_required")
     end
 
     def current_admin_account