feat: modernize landing page with shared design system

Replace custom CSS (831 lines, 16KB) with shared design system from
assets.21no.de. Net reduction of 841 lines.

Design changes:
- Background: #0f172a → #0a0a0b (canonical near-black)
- Fonts: Outfit + JetBrains Mono via assets.21no.de (self-hosted)
- Navigation: sticky with blur backdrop (shared nav.css)
- Hero: centered with radial glow, stats bar (5 metrics)
- Features: 6 cards in responsive grid with hover states
- Examples: 6 code snippets in dark cards with syntax highlighting
- Benchmarks: visual bar chart with rps comparison
- Configuration: styled table with monospace keys
- Fade-in scroll animations on all cards

Shared assets used:
- fonts.css, tokens.css, base.css, nav.css, hero.css
- buttons.css, cards.css, footer.css

Removed: docs/style.css (830 lines — fully replaced)

Author: molty3000