feat: add JWT authentication requirement to announcements retrieval endpoint.

Backend/src/controllers/announcementsController.ts

@@ -26,6 +26,7 @@ export class AnnouncementsController {
      * @param limit - จำนวนต่อหน้า / Items per page
      */
     @Get()
+    @Security('jwt')
     @SuccessResponse('200', 'Announcements retrieved successfully')
     @Response('401', 'Unauthorized')
     @Response('403', 'Forbidden')