Reliable connections on the Azure SQL Database container (pooling + retry)

Make the app's database connections reliable with connection pooling and retry / transient-fault handling. This is the Azure SQL engine (Private Preview), not the SQL Server image.

Verified on 2026-09-05 against the container image sqldbpreview-dpgaeqhmgphzd4bk.azurecr.io/azure-sql/db-dev:latest, reporting EngineEdition 5, Edition SQL Azure, build 12.0.2000.8. All five executable checks behind this skill passed: the engine identity, Msg 40508 for USE, a TCP session on the mapped port, and the two resource-governance dynamic management views returning nothing locally. Of the ten transient error numbers in the retry list below, nine are in this build's sys.messages and Msg 10929 is not. It stays in the list because it is a cloud resource-governance error the container has no reason to raise, and it is sourced from Microsoft Learn rather than from that run.

Why do this locally (local-to-cloud parity)