refactor: extract useSync hook from page.tsx

frontend/app/page.tsx

@@ -6,6 +6,7 @@ import { inventoryApi } from '@/lib/api';
 import { fetchAndCacheItems, syncOfflineOperations } from '@/lib/sync';
 import { useScanner } from '@/hooks/useScanner';
 import { useStockAdjustment } from '@/hooks/useStockAdjustment';
+import { useSync } from '@/hooks/useSync';
 import Scanner from '@/components/Scanner';
 import AIOnboarding from '@/components/AIOnboarding';
 import PageShell from '@/components/PageShell';
@@ -55,7 +56,6 @@ export default function Home() {
   const [isEditing, setIsEditing] = useState(false);
   const [editedItem, setEditedItem] = useState<Partial<Item>>({});
   const [trashReason, setTrashReason] = useState('Damaged');
-  const [syncing, setSyncing] = useState(false);
   const [currentUser, setCurrentUser] = useState<any | null>(null);
   const [categories, setCategories] = useState<any[]>([]);
   const [comparisonModal, setComparisonModal] = useState<{ show: boolean, newItem: any, existingItem: any, existingId: number | null }>({ show: false, newItem: null, existingItem: null, existingId: null });
@@ -106,6 +106,12 @@ export default function Home() {
     onInventoryUpdate: setInventory
   });
 
+  const { syncing, handleSync } = useSync({
+    isOnline,
+    currentUser,
+    onInventoryUpdate: setInventory
+  });
+
   useEffect(() => {
     if (!localStorage.getItem('inventory_token')) {
       window.location.href = '/login';
@@ -248,23 +254,6 @@ export default function Home() {
     loadInventory();
   };
 
-  const handleSync = useCallback(async () => {
-    if (!isOnline || !currentUser) return;
-    setSyncing(true);
-    try {
-      const result = await syncOfflineOperations(currentUser.id);
-      if (result.success > 0) {
-        toast.success(`Synced ${result.success} operations!`);
-      }
-      await loadInventory();
-    } catch (error) {
-      console.error("Sync failed", error);
-    } finally {
-      setSyncing(false);
-    }
-  }, [isOnline, currentUser]);
-
-
   const handleUpdateItem = async () => {
     if (!selectedItem) return;
     try {