test(ci): gate deployments on MariaDB and Redis integration checks

docs/testing/database-integration.md

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+# Real database integration tests
+
+Run `pnpm test:integration` on a Docker-capable host. Missing Docker or failed container setup fails the suite. CI runs this check before deployment.
+
+Six tests exercise real MariaDB catalog transactions and Redis caching: migration CLI replay/status, committed bulk edits and undo history, complete rollback when the second audit insert fails, competing previews, cache expiry metadata and cross-key invalidation isolation.
+
+Each execution starts disposable MariaDB11.4.5 and Redis7.4.2 containers with random exposed ports and generated passwords. No production URLs, volumes or credentials are used. The real migration CLI is copied beneath a temporary isolated fixture root so its environment loader cannot read the checkout environment file. Cleanup attempts all connections and containers even if a previous cleanup fails.
+
+The emulator fixture contains minimal catalog and audit tables. Migrations0027-0029 are exercised; this is not certification of every historical emulator schema or migration. Operation/outbox tests are introduced with their implementation in the following increment.