feat(kt): add key revocation and Merkle-log audit support
Add RevocationLog with domain-separated leaf hashes (0x02 prefix) for
tracking revoked identity keys alongside the KT MerkleLog. Includes:
- RevocationLog with O(1) lookup, serialization, and double-revoke guard
- MerkleLog.append_raw() for pre-computed hashes
- MerkleLog.audit_log(start, end) for paginated log retrieval
- RevokeKey (510), CheckRevocation (511), AuditKeyTransparency (520) RPCs
- Server domain logic + v2 handlers + FileBackedStore/SqlStore persistence
- 4 new revocation tests + all 21 KT tests + 65 server tests passing
Christian Nennemann
1768f85258