feat: move amenities directory to RoomCategoriesPage + cdn.hotelsync.ru for uploads

- Remove "Справочник удобств" block from RoomsPage, add to RoomCategoriesPage
- Fix RoomsPage imports (add Pencil back, remove unused amenity icons)
- Update hint in CategoryForm to point to current page
- Upload route now returns cdn.hotelsync.ru URLs instead of api.hotelsync.ru/uploads/
- Nginx config for cdn.hotelsync.ru (serves /opt/hotelsync/uploads directly)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/routes/upload.ts

@@ -31,10 +31,8 @@ const upload: FastifyPluginAsync = async (fastify) => {
 
       await pipeline(data.file, createWriteStream(filepath))
 
-      const host = (request.headers['x-forwarded-proto'] ?? 'https') + '://' +
-                   (request.headers['x-forwarded-host'] ?? request.headers.host ?? 'api.hotelsync.ru')
-
-      return { url: `${host}/uploads/${filename}` }
+      const cdnHost = process.env.CDN_HOST ?? 'cdn.hotelsync.ru'
+      return { url: `https://${cdnHost}/${filename}` }
     },
   )
 }