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/EmptyState.tsx

@@ -1,6 +1,6 @@
 'use client'
 
-import { ReactNode } from 'react'
+import { memo, ReactNode } from 'react'
 import { Inbox, ListTodo, Search, Filter } from 'lucide-react'
 
 interface EmptyStateProps {
@@ -10,7 +10,7 @@ interface EmptyStateProps {
   action?: ReactNode
 }
 
-export default function EmptyState({ icon = 'inbox', title, description, action }: EmptyStateProps) {
+function EmptyState({ icon = 'inbox', title, description, action }: EmptyStateProps) {
   const icons = {
     inbox: <Inbox size={48} className="text-gray-300" />,
     list: <ListTodo size={48} className="text-gray-300" />,
@@ -39,3 +39,5 @@ export default function EmptyState({ icon = 'inbox', title, description, action
     </div>
   )
 }
+
+export default memo(EmptyState)

components/FilterPanel.tsx

@@ -1,6 +1,6 @@
 'use client'
 
-import { useState } from 'react'
+import { memo, useState } from 'react'
 import { Filter, X, ChevronDown, ChevronUp } from 'lucide-react'
 
 export interface FilterState {
@@ -19,7 +19,7 @@ interface FilterPanelProps {
   showListScope?: boolean
 }
 
-export default function FilterPanel({ 
+function FilterPanel({ 
   filters, 
   onFiltersChange,
   availableTags = [],
@@ -294,3 +294,5 @@ export default function FilterPanel({
     </div>
   )
 }
+
+export default memo(FilterPanel)

components/ItemCard.tsx

@@ -1,5 +1,6 @@
 'use client'
 
+import { memo } from 'react'
 import Link from 'next/link'
 import { Calendar, Tag, AlertCircle } from 'lucide-react'
 import ToggleItemButton from './ToggleItemButton'
@@ -19,7 +20,7 @@ interface ItemCardProps {
   listId: string
 }
 
-export default function ItemCard({ item, listId }: ItemCardProps) {
+function ItemCard({ item, listId }: ItemCardProps) {
   const tags = Array.isArray(item.tags) ? item.tags : []
   const isOverdue = item.dueDate && new Date(item.dueDate) < new Date() && !item.completed
 
@@ -104,3 +105,5 @@ export default function ItemCard({ item, listId }: ItemCardProps) {
     </div>
   )
 }
+
+export default memo(ItemCard)

components/ListCard.tsx

@@ -1,7 +1,7 @@
 'use client'
 
+import { memo, useState } from 'react'
 import Link from 'next/link'
-import { useState } from 'react'
 import { Edit2 } from 'lucide-react'
 import Modal from './Modal'
 import ListForm from './ListForm'
@@ -17,7 +17,7 @@ interface List {
   }>
 }
 
-export default function ListCard({ list }: { list: List }) {
+function ListCard({ list }: { list: List }) {
   const [isEditModalOpen, setIsEditModalOpen] = useState(false)
   const completedCount = list.items.filter(item => item.completed).length
   const totalCount = list.items.length
@@ -94,4 +94,6 @@ export default function ListCard({ list }: { list: List }) {
       </Modal>
     </>
   )
-}
+}
+
+export default memo(ListCard)

components/ListDetailView.tsx

@@ -93,7 +93,9 @@ export default function ListDetailView({ listId, initialItems }: ListDetailViewP
         sortBy: newFilters.sortBy,
         sortOrder: newFilters.sortOrder
       })
-      setFilteredItems(results as Item[])
+      // Extract items from pagination result
+      const items = 'items' in results ? results.items : results
+      setFilteredItems(items as Item[])
     } catch (error) {
       console.error('Filter error:', error)
       setFilteredItems(initialItems)

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)

components/SearchResults.tsx

@@ -1,5 +1,6 @@
 'use client'
 
+import { memo } from 'react'
 import { highlightText } from '@/lib/utils'
 import Link from 'next/link'
 import { Calendar, Tag, AlertCircle } from 'lucide-react'
@@ -25,7 +26,7 @@ interface SearchResultsProps {
   onClose?: () => void
 }
 
-export default function SearchResults({ results, query, onClose }: SearchResultsProps) {
+function SearchResults({ results, query, onClose }: SearchResultsProps) {
   if (!query.trim()) {
     return null
   }
@@ -155,3 +156,5 @@ export default function SearchResults({ results, query, onClose }: SearchResults
     </div>
   )
 }
+
+export default memo(SearchResults)