[Medium] Implement Access Control contract

[Josie123-Dev]

Task Description

Create Access Control contract for credentials:

• Manage access permissions
• Control credential access
• Implement time-based access
• Add access revocation
• Track access logs

Requirements

• Permission management
• Access control
• Time-based access
• Revocation logic
• Access logging

Acceptance Criteria

• Permissions work
• Access is controlled
• Time limits work
• Revocation works
• Access is logged