Integration tests for revoked_certificates on hdb_nodes

## Request

The `hdb_nodes` table has a `revoked_certificates` array field (certificate serial numbers). Add integration tests:

1. Include `revoked_certificates` in an `add_node` call and verify a node using a revoked cert is rejected
2. Add a cert serial to `revoked_certificates` on an existing node and verify the cert is rejected on next connection attempt

🤖 Filed by Claude on behalf of Kris.