[Medium] Implement credential sharing with access control

[Josie123-Dev]

Task Description

Create credential sharing system with access control:

• Share credentials with specific addresses
• Set access permissions
• Implement time-limited access
• Add access revocation
• Track access logs

Requirements

• Create sharing records
• Implement permission checks
• Add time-based access control
• Implement revocation logic
• Log all access attempts

Acceptance Criteria

• Sharing works correctly
• Permissions are enforced
• Time limits work
• Revocation is immediate
• Access is logged completely

[Richiey1]

Hi maintainer! I'm a Stellar builder and I'm really enthusiastic about building secure, user-centric features! Implementing credential sharing with strict access controls is exactly the kind of challenge I love. I plan to build a flexible permission system that allows users to seamlessly share their credentials with granular time-limits or role-based restrictions, backed by rock-solid backend validation. I'd love to collaborate on getting this perfect. Ready to dive in once assigned!

[grantfox-oss]

🦊 GrantFox — @Richiey1 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #21)
2. Your PR will be reviewed by the GuardZero144 maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign | FWC26 campaign!

@Richiey1's PR #145 was approved and merged by @Josie123-Dev.

🏆 @Richiey1: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (379 total points). Track your full progress on GrantFox.

👏 Great work, @Richiey1! Keep contributing to GuardZero144.