Introduce comprehensive documentation of HAPI's Seamless Handoff feature:
- README: Add Seamless Handoff to Features section
- how-it-works: Add complete Seamless Handoff guide with local/remote modes and switching workflow
- quick-start: Add Seamless Handoff link to Next steps
- AppShowcase: Add third card featuring "Switch Freely" mode switching capability
- Locales: Update English and Chinese translations for showcase content
- Replace VitePress router with window.location for docs index redirect
- Add redirect rules for /docs and /docs/ paths to quick-start guide
- Simplify navigation by removing section anchor links
- Update all CTA buttons to link directly to /docs/ instead of home sections
- Consolidate navigation layout on both desktop and mobile views
- Set VitePress base to '/docs/' for serving documentation at /docs/ route
- Update favicon path in head config to '/docs/favicon.ico'
- Add build:site script to build website and docs, then merge outputs
weishu