Add Multi-Signature Authorization Support

[DevMuhdishaq]

Description

Implement multi-signature authorization to allow multiple authorized parties to approve high-value transactions for enhanced security.

Acceptance Criteria

• Multi-signature configuration structure created
• Support for 2-of-3 and 3-of-5 signature schemes
• Function to collect signatures from authorized signers
• Signature validation against public keys
• Threshold checking logic implemented
• Signature expiration mechanism (configurable timeout)
• Comprehensive tests for all signature combinations

Tasks

1. Design multi-sig data structure
2. Implement signature collection mechanism
3. Add threshold validation logic
4. Create signature expiration handling
5. Write integration tests