- Proper key type detection: Ed25519 (base64, 64 bytes) vs EC (PEM)
- Fixed PKCS8 fallback - removed incorrect PKCS8->EdDSA path for EC keys
- Added 'iat' claim to match official SDK
- Added base64 import for Ed25519 key decoding
- Return proper errors instead of ignoring them in GetAuthHeaders
- Added unit tests for EC/Ed25519 keys, token generation, and auth headers