feat: Product landing page at / with responsive design
- landing.html: Full product website (hero, features, how-it-works, platform coverage, pricing, FAQ, CTA, footer)
- main.py: Route / to landing.html (overrides StaticFiles default index.html)
- Workspace dashboard remains at /index.html
- Responsive: desktop nav, hamburger mobile menu, single-column on small screens
- No Vue/Element Plus dependency; standalone HTML+CSS+JS (~30KB)
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
Yuzhiran Dev
24e46eced5