Backend: extract Docker provisioning into @Async method so the API
returns immediately with status=PROVISIONING. The tenant record, Logto
org, admin user, and license are created synchronously; container
provisioning, health check, license push, and OIDC config happen in a
background thread.
Frontend: navigate to tenant detail page immediately after creation.
Detail page polls every 3s while status=PROVISIONING and shows a
spinner indicator. Toast notification when provisioning completes.
Fixes#52.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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