test(domain): expiry worker cancels the zaak via the ACL on timeout (refs #106)

S-10c: expiring the aggregate to VERLOPEN is not enough — the ZGW zaak must
also be cancelled through the ACL (§8.1). Adds IAclClient.CancelZaakAsync and
its client/fakes, and asserts the worker cancels a still-open registration's
zaak but leaves an already-resolved one untouched.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/acceptance/Support/InMemoryDomainPorts.cs

@@ -60,6 +60,14 @@ public sealed class InMemoryAclClient : IAclClient
         return Task.CompletedTask;
     }
 
+    public Uri? CancelledZaakUrl { get; private set; }
+
+    public Task CancelZaakAsync(Uri zaakUrl, CancellationToken ct = default)
+    {
+        CancelledZaakUrl = zaakUrl;
+        return Task.CompletedTask;
+    }
+
     public (Uri ZaakUrl, string FileName)? StoredDiploma { get; private set; }
 
     public Task<Uri> StoreDiplomaAsync(Uri zaakUrl, byte[] content, string fileName, string contentType, CancellationToken ct = default)