Fix: Remove unused import

The `startNetworkMonitoring` import was removed from `src/App.tsx` because it does not exist in the `syncUtils` module.

src/hooks/sync/useManualSync.ts

@@ -32,7 +32,7 @@ export const useManualSync = (user: any) => {
     
     try {
       setSyncing(true);
-      // 인자 수정: 콜백 함수 제거
+      // 인자 수정: userId만 전달
       const result = await trySyncAllData(userId);
       
       handleSyncResult(result);