Loads the registration, asks the ACL to set its zaak's final status (new
IAclClient.ApproveZaakAsync → POST /statussen), then advances the aggregate to
INGESCHREVEN. Idempotent: a repeated approval is a no-op. Adds HTTP-adapter tests.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>