Upgrade site to al-folio v1

[chenjunyan1]

Summary

• migrate site to al-folio v1 gem-based framework, preserving content and media
• keep People hidden from navigation and preserve unpublished content
• fix the homepage profile image and back-to-top control
• harden GitHub Pages CI with production builds, pinned PurgeCSS, and Node 24 actions

Validation

• npm ci
• Prettier checks
• npm run lint:style-contract
• JEKYLL_ENV=production bundle exec jekyll build
• npx purgecss -c purgecss.config.js
• bundle exec bin/al-folio upgrade audit (0 blocking, 4 nonblocking)
• desktop and mobile browser checks

[github-actions]

Failed prettier code check. Check this file for more information.