feat(infra): Flowable RegistratieVerlopen worker + document-wait completion (refs #102)

FlowableWorkflowClient implements IRegistratieVerlopenClient (acquire/complete the
RegistratieVerlopen jobs) and CompleteDocumentWaitAsync (complete WachtOpDocumenten,
best-effort). Wires the RegistratieVerlopenProcessor + hosted RegistratieVerlopenPump
into the domain host and excludes the pump from mutation (like the other pumps).
Fakes updated for the new IWorkflowClient member.

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

services/domain/Big.Tests/Fakes.cs

@@ -34,6 +34,7 @@ internal sealed class FakeWorkflowClient(string processInstanceId = "proc-1", Ac
     public RegistrationId? StartedFor { get; private set; }
     public DiplomaOrigin? StartedWithOrigin { get; private set; }
     public string? WithdrawnProcessInstanceId { get; private set; }
+    public string? CompletedDocumentWaitFor { get; private set; }
 
     public Task<string> StartRegistrationProcessAsync(
         RegistrationId registrationId, DiplomaOrigin diplomaOrigin, CancellationToken ct = default)
@@ -49,6 +50,12 @@ internal sealed class FakeWorkflowClient(string processInstanceId = "proc-1", Ac
         WithdrawnProcessInstanceId = processInstanceId;
         return Task.CompletedTask;
     }
+
+    public Task CompleteDocumentWaitAsync(string processInstanceId, CancellationToken ct = default)
+    {
+        CompletedDocumentWaitFor = processInstanceId;
+        return Task.CompletedTask;
+    }
 }
 
 /// <summary>A fake user-task client for the werkbak/decision use cases: returns a scripted set of