Detailed build contract for Subsystem B (15 customer-provisioning steps),
written against the real Subsystem-A contracts: ProvisioningStep/StepResult
(advance/retry/poll/fail), RunResource idempotency breadcrumbs, ProvisioningRun
context, the config/provisioning.php pipeline registry, and the read-only
ProxmoxClient it must extend. Covers new models (customers/orders/instances/…),
ProxmoxClient VM-lifecycle additions, Hetzner-DNS + Traefik services, Stripe
idempotent intake, live progress binding to the existing admin/customer views,
build order and DoD. Unblocks B.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>