Optimize bundle size with code splitting and lazy loading

Reduce initial bundle size from 800KB to under 300KB.

Actions

• Implement React.lazy() for route-based code splitting
• Split vendor chunks
• Use dynamic imports for heavy components
• Tree-shake unused dependencies
• Analyze bundle with webpack-bundle-analyzer

Target Metrics

• Initial bundle: < 300KB
• First Contentful Paint: < 1.5s
• Time to Interactive: < 3.5s