feat(landing): add Feishu community link

[kokisanai]

Summary

• add a Feishu entry immediately after Discord in the Community navigation
• add a prominent community button to the top-right navigation
• route Simplified and Traditional Chinese versions to Feishu (飞书社群 / 飛書社群)
• route every other language version to Discord (Discord)
• open community destinations in a new tab

Feishu tracking link

https://od.kokiai.net/community/website

Validation

• pnpm --filter @open-design/landing-page typecheck
• pnpm --filter @open-design/landing-page test
• pnpm --filter @open-design/landing-page build:static
• verified zh output renders the Feishu CTA and tracking link
• verified English and Japanese output render the Discord CTA and invite link
• verified the Feishu tracking link returns HTTP 302 to the group invite

[github-actions]

🚀 Landing page preview

This PR is deployed to a Cloudflare Pages preview — not staging or production:

• Stable alias: https://pr-6745.open-design-landing-staging.pages.dev
• This build: https://be070720.open-design-landing-staging.pages.dev
  Updated for commit 4ae919c.

[lefarcen]

Hey @kokisanai, the Summary section already gives enough context for the change itself. Could you add a Surface area section and tick UI for the landing-page header nav update so the PR body reflects the user-facing change? That should make it easier for the pool reviewer to scope this one.

[xxiaoxiong]

LGTM. Adds a Feishu community entry to the landing-page header — both as a dropdown item (alongside Discord) and as a top-right CTA, with locale-aware routing (zh / zh-tw → 飞书社群, others → Discord). Tracking via od.kokiai.net/community/website. CSS uses the existing coral pill pattern, has :focus-visible outline, and opens in a new tab via ext props. Self-contained to landing-page.

[xxiaoxiong]

LGTM — clean community link addition.

Verified: FEISHU URL constant added next to DISCORD, locale-aware switch (usesFeishuCommunity = locale === 'zh' || locale === 'zh-tw') drives the right-side CTA platform, with proper strings for 飞书社群 / 蹈書社群 / Discord. The dropdown menu gets both Discord and Feishu entries side-by-side. CSS uses --coral shared variable, includes hover state and focus-visible outline for accessibility. CTA has flex-shrink: 0 so it stays visible on narrow viewports.