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

next.config.js

@@ -1,8 +1,23 @@
 /** @type {import('next').NextConfig} */
 const nextConfig = {
   experimental: {
-    serverActions: true,
+    optimizePackageImports: ['lucide-react'],
   },
+  compiler: {
+    removeConsole: process.env.NODE_ENV === 'production' ? {
+      exclude: ['error', 'warn'],
+    } : false,
+  },
+  // Enable SWC minification for better performance
+  swcMinify: true,
+  // Optimize images
+  images: {
+    formats: ['image/avif', 'image/webp'],
+  },
+  // Enable compression
+  compress: true,
+  // Production source maps (smaller)
+  productionBrowserSourceMaps: false,
 }
 
 module.exports = nextConfig