Add stale audit grant pruning behavior

[edehvictor]

Summary

Add behavior for pruning expired audit grants without affecting active grants or historical audit references.

Why This Matters

Expired grants should not keep granting visibility, but pruning must not destroy evidence needed for later verification.

Suggested Files

• contracts/src/audit.rs
• contracts/src/storage.rs
• contracts/src/events.rs
• contracts/tests/audit_grant_pruning.rs

Tasks

• Identify expired audit grants by expiry timestamp.
• Add idempotent pruning for stale grants.
• Preserve digest references needed for audit history.
• Emit safe pruning events.

Acceptance Criteria

• Expired grants no longer authorize access.
• Active grants are not pruned.
• Historical digest references remain intact.
• Tests cover expired, active, and already-pruned grants.

Coordination

Join the Telegram channel for proper coordination: https://t.me/zkpayroll

[xtep103]

@xtep103 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hey Maintainer, I have gone through the details of the issue and i am capable of resolving it, I would love to be assigned to work on it ASAP. Thanks in advance

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[kuse-design]

@kuse-design has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

i would like to work on this issue, because am a software engineer and am capable of completing this task effectively.

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[mercy60]

@mercy60 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello, I'm a fullStack developer with years of experience, I have worked on several projects, can I please work on this.

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[TheHalalHunter]

@TheHalalHunter has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I would like to work on this issue because I have experience developing and testing smart contracts, specifically with state management and access controls. I can implement the pruning logic for stale audit grants, ensuring expired or unused authorizations are safely cleaned up without leaving orphaned state or security vulnerabilities.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @TheHalalHunter to this issue.

[dollfins]

@dollfins has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hey, I’d love to take this one on. I’m confident I can get it done.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @dollfins to this issue.

[drips-wave]

Congratulations, @TheHalalHunter! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @TheHalalHunter: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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[grantfox-oss]

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

@TheHalalHunter's PR #376 was approved and merged by @edehvictor.

🏆 @TheHalalHunter: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (223 total points). Track your full progress on GrantFox.

👏 Great work, @TheHalalHunter! Keep contributing to zkpayroll.

[drips-wave]

This issue has been marked as completed by a Drips Wave moderator for @TheHalalHunter as part of the Stellar Wave Program's 8th Wave 🥳

Moderator's reason: [Auto-assessed] The PR was merged by maintainer @edehvictor on 2026-08-28 as recorded in the merge event and issue completion announcement. The code changes correctly implement stale audit grant pruning with batch limiting, idempotency, tombstone recording, and event emission.

😎 @TheHalalHunter: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here.

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ℹ️ Note: This issue was marked complete via moderation. Points were issued even though the GitHub issue remains open.