Complete Android-first UI rebuild with mobile-first design system

Rebuild UI: complete redesign with accessibility, responsiveness, and bug fixes

feat: upgrade Android responsiveness, SEO, mobile UX across all frontend files

feat: complete project publishing, ai chat, and mobile terminal enhancements

style: fix mobile responsiveness for android viewports

feat: redesign ui with themes, icons, toasts, and live preview

Create static/css/variables.css