Introduce a Reqnroll.xUnit acceptance project under tests/acceptance/ and
the first Gherkin scenario driving S-04: the ACL default-fills the
ZGW-mandatory zaak fields (ADR-0003) from a domain registration payload.
Red: the scenario is discovered but has no step bindings yet, so it fails
with undefined steps. The green commit wires the bindings to AclService.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
