Function sign_dsa 

pub fn sign_dsa(
    secret_key: &[u8],
    message: &[u8],
) -> Result<Signature, CryptoError>

Sign message with the ML-DSA-87 secret key (32-byte seed).

Signing is deterministic — no per-call randomness required.

Errors

Returns CryptoError::InvalidKeyLength if secret_key is not 32 bytes. Returns CryptoError::SigningFailed if the deterministic signing operation fails.