Fix synthesis loading from database

- useQuery now returns data properly
- useEffect sets synthesis state when loadedSynthesis changes
- Synthesis will persist across page refreshes
- No dependency on synthesis in useEffect (prevents loops)

Synthesis persistence NOW WORKING!

frontend/src/app/notebooks/[id]/page.tsx

@@ -65,21 +65,28 @@ export default function NotebookDetailPage() {
   });
 
   // Load saved synthesis from database
-  useQuery({
+  const { data: loadedSynthesis } = useQuery({
     queryKey: ['synthesis', notebookId],
     queryFn: async () => {
       try {
         const response = await notebookAPI.getSynthesis(notebookId);
         if (response.data && response.data.status !== 'none') {
-          setSynthesis(response.data);
+          return response.data;
         }
-        return response.data;
+        return null;
       } catch {
         return null;
       }
     },
   });
 
+  // Set synthesis from loaded data
+  useEffect(() => {
+    if (loadedSynthesis && !synthesis) {
+      setSynthesis(loadedSynthesis);
+    }
+  }, [loadedSynthesis]);
+
   const synthesisMutation = useMutation({
     mutationFn: async () => {
       const response = await notebookAPI.generateSynthesis(notebookId);