feat(event-subscriber): project a status-set as INGESCHREVEN via hoofdObject (refs #75)

Bind the NRC hoofdObject, recognise a zaken/status/create notification, and key the
projection on the zaak (hoofdObject) so the status updates the existing INGEDIEND row
to INGESCHREVEN — without reading OpenZaak (§8.1). Retain the ZGW resource in the log
(new column + migration) so a rebuild reproduces the approved status. Updates the
acceptance fakes for the new IAclClient/IZaakGateway members.

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

services/event-subscriber/EventSubscriber.Application/RegisterEntry.cs

@@ -17,4 +17,7 @@ public static class RegistrationStatus
 {
     /// <summary>A zaak has been created; the registration is submitted.</summary>
     public const string Ingediend = "INGEDIEND";
+
+    /// <summary>The registration has been approved and entered in the register (S-09b).</summary>
+    public const string Ingeschreven = "INGESCHREVEN";
 }