Signature Verification Security

Analyze the signature verification implementation in this contract:

```
${{CONTRACT_CODE}}
```

Signature Use Cases: ${{USE_CASES}}

Security review:
1. Signature scheme analysis (ECDSA, EIP-712)
2. Vulnerability identification:
   - Signature replay attacks
   - Cross-chain replay
   - Signature malleability
   - Missing nonce handling
3. EIP-712 compliance check
4. Domain separator implementation
5. Deadline/expiration handling
6. Signer validation
7. Recommended fixes:
   - Proper nonce management
   - Chain ID inclusion
   - Structured data hashing
8. Test vectors for verification
9. Integration with meta-transactions

Provide secure implementation examples.