Improve real-time sync with 1-second polling and visual indicator

- Reduced polling interval from 2s to 1s for near-instant updates
- Added SyncIndicator component to show sync status
- Added console logging to debug sync behavior
- Updates across devices now appear within 1 second
- Visual feedback shows when data is being refreshed

hooks/useRealtimeSync.ts

@@ -24,11 +24,12 @@ export function useRealtimeSync({
   const intervalRef = useRef<NodeJS.Timeout | null>(null)
 
   const refresh = useCallback(() => {
+    console.log('[RealtimeSync] Refreshing...', listId ? `list ${listId}` : 'page')
     router.refresh()
     if (onUpdate) {
       onUpdate()
     }
-  }, [router, onUpdate])
+  }, [router, onUpdate, listId])
 
   useEffect(() => {
     if (!enabled) {