Add ETH Key Support to SIWF (Sign-In With Framework)

[p5150j]

Description

Extend the Sign-In With Frequency functionality to support Ethereum keys and signatures, enabling seamless authentication.

Tasks

• Update SIWF message format to be compatible with ETH signing
• Implement ETH signature verification in SIWF
• Update frontend components to support ETH wallet connections
• Create documentation for developers integrating with SIWF using ETH

Acceptance Criteria

• [ ] SIWF accepts and verifies ETH signatures
• [ ] Authentication flow works end-to-end with ETH keys
• [ ] Frontend components display correctly for ETH connections
• [ ] Documentation updated with ETH-specific integration guidelines
• [ ] Test suite covering ETH authentication scenarios
• [ ] Security review of ETH implementation completed