Rehearse and execute the modernized production rollout with a tested rollback

[coder13]

Goal

Ship the Node 22, Vite, MongoDB 7, Redis, Docker Compose, and PostgreSQL dual-write stack without making production the first full migration test.

Acceptance criteria

• Complete the integrated release candidate in Integrate the remaining modernization work on dev and cut a release candidate #173.
• Capture a fresh MongoDB backup and successfully restore it into a non-production rehearsal environment.
• Rehearse the Compose deployment, Prisma migrate deploy, API/socket startup, and health checks using production-shaped configuration.
• Verify login, room create/join/rejoin, spectating, result submission/editing, room expiry, and Redis-backed multi-process Socket.IO behavior.
• Configure PostgreSQL credentials, METRICS_HASH_SECRET, retention, TLS/CA settings where applicable, and confirm secrets are not logged.
• Define rollback triggers and rehearse rollback to the previous app revision without deleting or downgrading data.
• Promote the reviewed dev → master release and monitor API/socket errors, auth failures, room events, PostgreSQL write failures, and resource use.
• Record the deployed commit and post-deploy verification results.

References

• README_DEPLOYMENT.md
• PR Add PostgreSQL dual writes and room metrics #171
• Integrate the remaining modernization work on dev and cut a release candidate #173
• Test dev merge commits and document the dev-to-master release workflow #177