feat: async tenant provisioning with polling UX

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>

ui/src/api/vendor-hooks.ts

@@ -10,11 +10,15 @@ export function useVendorTenants() {
   });
 }
 
-export function useVendorTenant(id: string | null) {
+export function useVendorTenant(
+  id: string | null,
+  options?: { refetchInterval?: number | false | ((query: { state: { data: VendorTenantDetail | undefined } }) => number | false) },
+) {
   return useQuery<VendorTenantDetail>({
     queryKey: ['vendor', 'tenants', id],
     queryFn: () => api.get(`/vendor/tenants/${id}`),
     enabled: !!id,
+    refetchInterval: options?.refetchInterval as any,
   });
 }