Bespoke fun landing layout + funnier shared theme

Replace the plain VitePress home with the bespoke Claude Design landing,
ported as a full-page VitePress layout (apps/website Landing.vue,
index.md layout:false):
- custom sticky header, floating beetroot + glow hero, philosophy cards,
  package cards with SVG project logos, click-to-copy install commands
  (toast), live GitHub stars, CTA banner and footer.

Push the same playfulness into @btravstack/theme so the docs sites match:
home-hero beetroot glow + floating logo, lifting feature cards, springy
brand buttons, rounder/pinker code. Verified on standard VitePress chrome
in light and dark.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: btravers