Document Community Watch production rollout dependencies

[mashbean]

Summary

Tighten the production rollout checklist before Community Watch goes live on production.

Changes:

• document the web production release PR dependency
• document that the server retention follow-up is already merged to develop
• make the production GraphQL schema check explicit before switching the public site to production data
• align the public API contract with the current Cache-Control: no-store behavior

Validation

Docs-only change. Earlier production-prep verification on the same branch passed:

• pnpm typecheck
• pnpm build

Rollout note

Do not merge this as a substitute for production approval. The server and web production release PRs still need explicit review and human approval before production rollout.