Add Bun bundler for frontend JavaScript

- Bundle all frontend JS with Bun.build() (82KB minified)
- Dependencies (motion, lenis, three) are now bundled instead of CDN
- Remove import map from index.html (no longer needed)
- Output to public/dist/app.bundle.js with source map
- Add public/dist/ to .gitignore (generated during build)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -4,6 +4,7 @@ node_modules/
 # Generated files
 dist/*.zip
 public/css/styles.css
+public/dist/
 
 # Build artifacts
 *.log