GLACIS Demo Medical Chat API - REAL Cryptographic Attestations

Every message generates:
✓ Real SHA-256 cryptographic hash
✓ Real attestation appended to Merkle tree at attestation-log.glacis.io
✓ Real epoch tracking from witness.glacis.io
✓ Verifiable transparency log entry

Current Merkle tree: 1899 leaves

Endpoints:
- GET /stats - Demo statistics with real Merkle tree data
- GET /recent - Recent messages with attestation IDs
- POST /send - Send message (generates REAL attestation)
- GET /merkle/stats - Real-time Merkle tree statistics