feat(acl): gateway cancels a zaak via Geannuleerd status + Vervallen resultaat (refs #106)

SetZaakToCancellationStatusAsync resolves the cancellation statustype and
resultaat by omschrijving and posts resultaat-then-status, mirroring the
approval path. Approval now resolves its Geregistreerd resultaat by name too,
since a second resultaattype now exists.

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

services/acl/Acl.Tests/OpenZaakGatewayTests.cs

@@ -410,7 +410,7 @@ public class OpenZaakGatewayTests
             Gateway(ApprovalStub(rec, new OzRoutes { ResultaattypenJson = "{}" }))
                 .SetZaakToEindstatusAsync(new Uri(ZaakUrl), Zaaktype, new DateOnly(2026, 6, 4)));
 
-        Assert.Contains("No resultaattypen found", ex.Message);
+        Assert.Contains("'Geregistreerd' resultaattype", ex.Message);
         // Resolved the eindstatus + queried resultaattypen, but posted nothing.
         Assert.Equal(-1, rec.IndexOf("/resultaten"));
         Assert.Equal(-1, rec.IndexOf("/statussen"));