feat: implement performance optimizations

- Add database indexes for frequently queried fields (listId, completed, priority, dueDate, createdAt)
- Add compound indexes for common query patterns (listId+completed, listId+priority)
- Implement pagination support in getItemsByFilter with configurable page size (default 50)
- Optimize components with React.memo (ItemCard, ListCard, FilterPanel, SearchBar, SearchResults, EmptyState)
- Configure Next.js for better bundle optimization:
  - Enable optimizePackageImports for lucide-react
  - Enable SWC minification
  - Remove console logs in production (except errors/warnings)
  - Optimize images with AVIF/WebP formats
  - Enable compression
  - Disable production source maps for smaller bundles
- Loading states already implemented to prevent layout shift

Task 18 complete - all performance optimizations implemented

components/SearchBar.tsx

@@ -1,5 +1,6 @@
 'use client'
 
+import { memo } from 'react'
 import { Search, X } from 'lucide-react'
 import { useSearch } from '@/hooks'
 
@@ -10,7 +11,7 @@ interface SearchBarProps {
   initialValue?: string
 }
 
-export default function SearchBar({ 
+function SearchBar({ 
   onSearch, 
   placeholder = 'Search tasks...', 
   debounceMs = 300,
@@ -53,3 +54,5 @@ export default function SearchBar({
     </div>
   )
 }
+
+export default memo(SearchBar)