Rebuild cheat sheet as standalone HTML page

Replaces MkDocs markdown page with a flashy standalone page featuring:
- Dark/light mode toggle with system preference detection
- Sticky header row and sticky first column for scrolling
- Rounded corners, hover effects, gradient accents
- GRC Engineering orange/blue color scheme
- Fully responsive layout

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

Author: 3 people