Tests MILESTONES.md acceptance criterion #6: peer add flow yields an
active peer record with a valid cert + key. Simulates two gateways
against a single NestJS app instance with FederationModule + overridden
AdminGuard. Steps: keypair → enrollment → cert storage → DB assertion.
Gated by FEDERATED_INTEGRATION=1 and STEP_CA_AVAILABLE=1.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
