chore: rotate IndexNow verification key

[EmersonBraun]

Summary

• rotate the public IndexNow ownership verification file
• preserve the existing submission workflow and script unchanged
• unblock Bing verification after the previous key returned SiteVerificationNotCompleted

Validation

• verification file is UTF-8 text and contains the matching 32-character key
• only the old and new verification files changed
• git diff --check passes
• docs:bridge:gate reaches the pre-existing ecosystem cross-links failure; this operational file change does not affect that manifest

Rollout

After preview verification, update the existing INDEXNOW_KEY Actions secret. Merge only after required checks pass; the normal production deployment will trigger one IndexNow workflow run.

[github-actions]

Lighthouse

URL	Performance	Accessibility	Best practices	SEO
http://127.0.0.1:3000/	52	92	96	100
http://127.0.0.1:3000/docs	68	100	96	100
http://127.0.0.1:3000/docs/get-started/getting-started/quickstart	66	96	96	100
http://127.0.0.1:3000/stack	90	100	96	100
http://127.0.0.1:3000/showcase	90	100	96	100

Run by .github/workflows/lighthouse.yml.