feat(domain): ProvideDocuments stores the diploma via the ACL then completes the wait (refs #103)

IAclClient.StoreDiplomaAsync + AclHttpClient (base64 JSON to the ACL /documenten
endpoint). ProvideDocuments stores the uploaded bytes against the zaak (when opened)
before completing WachtOpDocumenten; the domain endpoint accepts the file base64-encoded.

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

services/domain/Big.Application/Ports.cs

@@ -52,6 +52,13 @@ public interface IAclClient
     /// the zaak's final status — which OpenZaak notifies over NRC; the domain never names statustypen.
     /// </summary>
     Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default);
+
+    /// <summary>
+    /// Store an uploaded diploma against the zaak (S-10b). The domain hands over the zaak, the raw file
+    /// bytes, and the file's name/type; the ACL creates the ZGW informatieobject and relates it to the
+    /// zaak (§8.1). Returns the stored document's URL.
+    /// </summary>
+    Task<Uri> StoreDiplomaAsync(Uri zaakUrl, byte[] content, string fileName, string contentType, CancellationToken ct = default);
 }
 
 /// <summary>