feat: migrate graph snapshot handling to localStorage for improved persistence

src/hooks/useGraphData.js

@@ -52,11 +52,10 @@ export function useGraphData() {
 
   // On mount, check whether a snapshot from a previous session exists.
   useEffect(() => {
-    db.getGraphSnapshot().then(snap => {
-      if (snap?.ts) {
-        setSnapshotMeta({ ts: snap.ts, topicCount: snap.topicCount, relationCount: snap.relationCount });
-      }
-    });
+    const snap = db.getGraphSnapshot();
+    if (snap?.ts) {
+      setSnapshotMeta({ ts: snap.ts, topicCount: snap.topicCount, relationCount: snap.relationCount });
+    }
   }, []);
 
   // ── Single-topic mutations ───────────────────────────────────────────────────
@@ -124,7 +123,7 @@ export function useGraphData() {
    */
   const bulkSave = useCallback(async (newTopics, newRelations) => {
     // Persist a rollback point of the state we are about to overwrite.
-    await db.saveGraphSnapshot(topicsRef.current, relationsRef.current);
+    db.saveGraphSnapshot(topicsRef.current, relationsRef.current);
     setSnapshotMeta({
       ts: Date.now(),
       topicCount: topicsRef.current.length,
@@ -145,7 +144,7 @@ export function useGraphData() {
    * Returns true on success, false if no snapshot exists.
    */
   const restoreSnapshot = useCallback(async () => {
-    const snap = await db.getGraphSnapshot();
+    const snap = db.getGraphSnapshot();
     if (!snap?.topics) return false;
 
     // Apply without taking a new snapshot — we don't want to overwrite
@@ -155,7 +154,7 @@ export function useGraphData() {
     setTopics(snap.topics);
     setRelations(snap.relations);
 
-    await db.clearGraphSnapshot();
+    db.clearGraphSnapshot();
     setSnapshotMeta(null);
     return true;
   }, []);