fix: Display network error on API fetch failure

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

webclient/src/Feed.js

@@ -10,7 +10,12 @@ function Feed({ updateCache }) {
 
 	useEffect(() => {
 		fetch('/api')
-			.then(res => res.json())
+			.then(res => {
+				if (!res.ok) {
+					throw new Error(`Server responded with ${res.status} ${res.statusText}`);
+				}
+				return res.json();
+			})
 			.then(
 				async (result) => {
 					const newApiStories = result.stories;