redesign(landing): full homepage redesign with split hero layout

- Replace ASCII logo with split layout: left copy + right terminal mockup
- Add CSS-only macOS terminal window showing TUI preview
- Fix CTA hierarchy: install command primary, Get Started solid, GitHub outline
- Add dynamic GitHub star count badge
- Polish preset cards with shadows, pill badges, softer corners
- Animate snapshot section gradient border
- Add subtle page background gradient
- Update footer with tagline
- Both dark and light themes verified

Author: fullstackjam