Aggiunge annunci in-app/sito, contatti e migliora UI copertina sul portale.

Include admin/API/banner nativi, form contatti e reset copertina standard con layout edit più ampio.

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

backend/app/controllers/api/v1/announcements_controller.rb

@@ -0,0 +1,13 @@
+module Api
+  module V1
+    class AnnouncementsController < BaseController
+      skip_before_action :authenticate_request!
+
+      def index
+        platform = params[:platform].to_s.presence
+        announcements = AppAnnouncement.for_app.newest
+        render json: announcements.map { |item| item.as_api_json(platform: platform) }
+      end
+    end
+  end
+end