feat(website): migrate docs from Nuxt to Vite, rename to website

- Remove Nuxt project (docs/) entirely
- Create website/ with Vite + Vue 3 + vue-router + Tailwind (same versions as app)
- Port landing page: replace NuxtLink→RouterLink, Icon (abckit)→@iconify/vue, remove useHead
- Port docs pages: [slug].vue and channels/[type].vue with same VitePress-style layout
- Add docs/layout.vue: sticky sidebar with Guide/Features/Reference groups and collapsible Channels
- Share markdown files from app/src/docs/ via relative import.meta.glob paths
- Copy DocsCodeBlock and useDocsComponents composable from app (zero divergence)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: productdevbook