Mirror of DEV_CUTOVER_RUNBOOK.md adjusted for optical-prod:
* Step 1 covers the merge-to-main + tag v3.0.0 done from the laptop
before any server-side work begins.
* Reflects the gotchas we hit on Dev (per-repo Bitbucket Access Key,
docker group membership, SSH alias, .env from .env.prod.example,
Apache Include pattern).
* Adds post-cutover housekeeping: daily DB backup cron, disk-usage
warning cron, and the sandbox decommission steps for optical-web-1
after the 1-week soak.
