fix: Improve error handling for non-JSON server responses in Submit

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

webclient/src/Submit.js

@@ -17,7 +17,18 @@ function Submit() {
 		data.append('url', url);
 
 		fetch('/api/submit', { method: 'POST', body: data })
-			.then(res => res.json().then(data => ({ ok: res.ok, data })))
+			.then(res => {
+				if (res.ok) {
+					return res.json().then(data => ({ ok: true, data: data }));
+				}
+				// Handle error responses
+				return res.json()
+					.then(data => ({ ok: false, data: data })) // Our API's JSON error
+					.catch(() => {
+						// Not a JSON error from our API, so it's a server issue
+						throw new Error(`Server responded with ${res.status} ${res.statusText}`);
+					});
+			})
 			.then(
 				({ ok, data }) => {
 					if (ok) {