feat(docs): redesign homepage with liquid glass visuals

[stackia]

Summary

• redesign the Chinese and English documentation homepages with responsive liquid-glass surfaces, ambient lighting, shadows, and motion
• preserve the existing feature content, demo videos, dashboard screenshots, and localized guidance in a new glass card layout
• add a scoped VitePress theme with dark mode, reduced-motion, mobile navigation, and backdrop-filter fallbacks

Test plan

• Run pnpm run docs:build
• Run Biome checks for the custom VitePress theme
• Verify Chinese and English homepages in light and dark modes
• Verify desktop and mobile layouts, including the mobile navigation menu

[github-actions]

Documentation preview

The documentation preview has been deployed for this pull request.

• Preview: https://thankful-water-0a297bf00-644.eastasia.1.azurestaticapps.net
• Commit: 6a80e8a

[chatgpt-codex-connector]

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