Azure: B-series restricted per-subscription; IMDS public IP empty

On some Azure subscriptions, az vm create fails with SkuNotAvailable/capacity, and az vm list-skus shows B-series and Dv5/Dv6 families as NotAvailableForSubscription with a type:Location restriction (not just Zone) — even though vCPU quota is 65 and unused. The fix is to pick a v7 family (e.g. Standard_D2as_v7) which deploys fine. Separately, the Azure IMDS endpoint (169.254.169.254 .../publicIpAddress) frequently returns an EMPTY string, silently breaking hostname derivation in provisioning scripts — pass the known public IP explicitly instead.