feat(contact): add discord link

[yigitdot]

What

Adds the deCDN Discord (https://discord.gg/vVbNswKVGX) everywhere the other social profiles already appear:

• lib/links.ts — new links.discord, the single source of truth.
• Contact section (components/site/Contact.tsx) — discord link with a Simple Icons (CC0) glyph, beside github in the second row. Same markup as the other social links (underline-brutal, new tab, noopener noreferrer).
• Organization JSON-LD (lib/schema.ts) — appended to sameAs; new assertion in lib/schema.test.ts pins the full list.
• llms-full.txt — appended to the contact line.
• docs/docs.json — added to Mintlify footer.socials and the organization sameAs.

Why

New community channel; it should be discoverable from the site, the structured-data graph, the LLM mirror and the docs.

Notes for reviewers

• No CSP change needed: it's an outbound link, not a fetch.
• Nav and footer carry no socials today, so they're untouched.
• docs.json ships via the separate Mintlify pipeline.

Verification

• pnpm typecheck, pnpm lint, pnpm test (521 passing), pnpm format:check
• pnpm build incl. check:out / check:og-image; confirmed the link, JSON-LD sameAs and llms-full line in out/
• Visually checked #contact at desktop and 375px mobile widths

🤖 Generated with Claude Code

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[cloudflare-workers-and-pages]

Deploying website with    Cloudflare Pages

Latest commit:	75bfffd
Status:	✅  Deploy successful!
Preview URL:	https://8bd7df06.website-70y.pages.dev
Branch Preview URL:	https://claude-add-discord-link-4c6f.website-70y.pages.dev

View logs