Add real-time updates and fix delete button state

- Simplified useRealtimeSync to use router.refresh() polling
- Created RealtimeUpdater component for easy integration
- Added real-time updates to home page (3s polling)
- Fixed DeleteItemButton to properly reset state on error
- Updates now refresh every 3 seconds and on window focus
- Changes from other users/browsers will appear quickly

hooks/useRealtimeUpdates.ts

@@ -0,0 +1,37 @@
+'use client'
+
+import { useEffect, useCallback } from 'react'
+import { useRouter } from 'next/navigation'
+
+/**
+ * Hook for real-time updates via polling
+ * Refreshes data at regular intervals to show changes from other users/browsers
+ */
+export function useRealtimeUpdates(intervalMs: number = 3000) {
+  const router = useRouter()
+
+  const refresh = useCallback(() => {
+    router.refresh()
+  }, [router])
+
+  useEffect(() => {
+    // Poll for updates
+    const interval = setInterval(() => {
+      refresh()
+    }, intervalMs)
+
+    // Also refresh when window regains focus
+    const handleFocus = () => {
+      refresh()
+    }
+
+    window.addEventListener('focus', handleFocus)
+
+    return () => {
+      clearInterval(interval)
+      window.removeEventListener('focus', handleFocus)
+    }
+  }, [intervalMs, refresh])
+
+  return { refresh }
+}