feat: Performance optimization and CI/CD improvements

New Files

Components

• src/components/shared/HeroImage.tsx - Optimized hero image with LCP priority settings
• src/components/manage/LazySelectableGrid.tsx - Lazy wrapper for @dnd-kit components

Utilities

• src/utils/photoswipe.ts - Lazy loader for PhotoSwipe lightbox

SEO

• src/app/sitemap.ts - Dynamic sitemap generation
• src/app/robots.ts - Robots.txt configuration

CI/CD

• .husky/pre-commit - Pre-commit hooks (lint, typecheck, tests)

Documentation

• docs/performance-optimization.md - Performance best practices guide

Modified Files

Configuration

• next.config.ts - Added security headers, CSS optimization, AVIF/WebP formats, bundle analyzer
• package.json - Added scripts (analyze, typecheck, test:run, lint:fix), husky, lint-staged, cross-env

Components (Lazy Loading)

• src/components/photo/PhotoWithLightbox.tsx - Use lazy PhotoSwipe loader
• src/components/manage/PhotoListItem.tsx - Use lazy PhotoSwipe loader
• src/components/photo/FullSizeGalleryButton.tsx - Use lazy PhotoSwipe loader
• src/components/shared/ClickableAvatar.tsx - Use lazy PhotoSwipe loader
• src/components/manage/PhotoGrid.tsx - Use LazySelectableGrid
• src/components/manage/AlbumGrid.tsx - Use LazySelectableGrid
• src/app/admin/events/[eventId]/page.tsx - Inline dynamic import for exifr

Accessibility

• src/components/layout/Footer.tsx - Add aria-labels to social buttons
• src/components/photo/JustifiedPhotoGrid.tsx - Add aria-labels to photo links
• src/components/events/EventCard.tsx - Fix color contrast on upcoming badge

Pages

• src/app/page.tsx - Server-side hero image selection, HeroImage component
• src/app/members/page.tsx - Add Suspense boundaries for streaming

CI/CD

• .github/workflows/ci.yml - Add lint-and-typecheck job before tests

Documentation

• README.md - Add pre-commit hooks and CI pipeline docs
• docs/README.md - Add link to performance guide