Tamper-evident audit logging

[yaront1111]

Repo: cordum

Problem

SECURITY.md claims append-only, tamper-evident audit logging, but audit data is stored in Redis lists/config without integrity chaining.

Proposed

• Add an audit log store that writes append-only records with hash chaining and optional HMAC.
• Record key security events (policy publish/rollback, approvals, auth changes).
• Provide a verify endpoint/utility.

Acceptance

• Audit records include prev_hash and hash (and optional HMAC).
• Verification detects tampering or missing entries.
• Docs updated with retention and key management guidance.

References

• core/controlplane/gateway/policy_bundles.go
• core/workflow/store_redis.go
• SECURITY.md