feat: add short link to create endpoint response

Enhances the link creation API response by including a formatted short link URL
Combines protocol, host, and slug to create a complete, ready-to-use short URL

server/api/link/create.post.ts

@@ -23,6 +23,7 @@ export default eventHandler(async (event) => {
       },
     })
     setResponseStatus(event, 201)
-    return { link }
+    const shortLink = `${getRequestProtocol(event)}://${getRequestHost(event)}/${link.slug}`
+    return { ...link, shortLink }
   }
 })