- Expanded database schema to include `leaf_hash` in `audit_records` and added `audit_sths` table.
- Implemented `server/audit_merkle.ts` for native WebCrypto RFC 6962 tree computations and inclusion proofs.
- Created asynchronous micro-batcher in `server/audit.ts` to compute STH, sign with SPIFFE key, save to DB, and broadcast via Valkey.
- Refactored `auditLog` to compute leaf hashes synchronously before database inserts.
- Added hermetic unit tests with mock fallback patterns for SPIFFE/FFI in `server/audit_merkle.test.ts`.
Co-authored-by: mrteye <1945243+mrteye@users.noreply.github.com>