Azure: allow overriding the CD storage account / blob container (equivalent of --bucket / DEFANG_CD_BUCKET)

[defangdevs]

Summary

AWS, GCP, and DigitalOcean BYOC let you adopt an existing CD state bucket instead of creating a new one, via defang cd install --bucket <name> / the DEFANG_CD_BUCKET env var (see #2194). Azure has no equivalent because its CD/Pulumi state doesn't live in a bucket — it lives in a Storage Account + Blob Container (d.StorageAccount / d.BlobContainerName in src/pkg/clouds/azure/cd/). So --bucket is intentionally rejected for Azure today.

Ask

Add an Azure equivalent so a pre-existing CD state store can be adopted (and re-used across teardown/re-bootstrap, avoiding churn/orphaning):

• a --storage-account and/or --container override on defang cd install (Azure-appropriate names), and/or
• corresponding env vars (e.g. DEFANG_CD_STORAGE_ACCOUNT / DEFANG_CD_CONTAINER), mirroring how DEFANG_CD_BUCKET works for the object-storage clouds.

Note Azure storage-account names are globally unique and have their own naming rules, so this shouldn't be overloaded onto --bucket.

Context / related

• fix(cd): adopt an existing CD state bucket instead of creating a new one #2194 — implements --bucket / DEFANG_CD_BUCKET adoption for AWS, GCP, DigitalOcean (explicitly excludes Azure).
• BYOC AWS: re-bootstrapping mints a new defang-cd CD bucket each time and orphans the old one (bucket leak) #2192 — CD bucket churn / orphaned buckets (the problem adoption solves).
• Defang cd init with previous s3 bucket #358 / reuse cd bucket #422 — original "reuse cd bucket" for the old ECS CD (later reverted; not carried into the CodeBuild CD).
• #2707 — use the CD stack from any region (related region-coupling).
• BYOC AWS: region resolved from AWS_DEFAULT_REGION before AWS_REGION → cross-region cd down hits the wrong region #2191 — CD region-precedence bug (adjacent CD-bootstrap fix).