perf: site performance optimization

[Xixn2]

Summary

Investigate and fix performance bottlenecks:

• Audit animation performance (GPU compositing, will-change)
• Reduce JS bundle size (dynamic imports, tree shaking)
• Image optimization (WebP/AVIF, lazy loading, sizes)
• Eliminate layout shift (CLS)
• Reduce LCP time
• Remove redundant re-renders in React components