add form validation

frontend/src/app/nominations/page.tsx

@@ -14,6 +14,9 @@ export default function Nominations() {
   const [songURL, setSongURL] = useState("");
   const [isLoading, setIsLoading] = useState(false);
   const [message, setMessage] = useState("");
+  const isSpotifyURL =
+    /^https:\/\/open\.spotify\.com\/track\/[a-zA-Z0-9]{22}/.test(songURL);
+
   async function nominate(spotifyLink: string) {
     try {
       setIsAnimate(false);
@@ -54,7 +57,7 @@ export default function Nominations() {
           <button
             className="w-full rounded bg-blue-500 px-4 py-2 text-center font-bold text-white hover:bg-blue-400 disabled:cursor-not-allowed disabled:bg-gray-500"
             type="submit"
-            disabled={isLoading || !songURL.trim()}
+            disabled={isLoading || !songURL.trim() || !isSpotifyURL}
             onClick={async (e) => {
               e.preventDefault();
               if (!songURL.trim()) return;