[40] Add persistent storage rent sweep / reclaim path

[merlik787-droi]

Problem Statement

Soroban storage requires explicit TTL management. With no off-ramp, abandoned storage entries (learner progress on completed courses, old DataKey::Submission, refunded quest records, revoked badge entries) accumulate and rent-charges continue invisibly.

There is no contract-internal sweep/recovery mechanism today.

Why It Matters

• Long-term protocol sustainability depends on storage costcontrol.
• Without sweeps, the storage footprint grows monotonically.

Expected Outcome

• New admin-only function sweep_storage(env, admin, sweep_learning_keys: bool):
  • Iterates or samples for abandoned storage entries.
  • Removes or extends TTL based on policy.
• New view function estimated_storage_footprint(env) -> u32 (count).
• Document cost-benefit tradeoffs.

Acceptance Criteria

• Tests confirm sweep removes targeted entries.
• estimated_storage_footprint matches expected count.

Implementation Notes

• Soroban doesn't expose a "scan storage" API; survey-style implementation needs custom indexes.
• Tie to Issue [19] Add storage TTL handling analysis and bump-on-touch for all persistent reads #19 (TTL bumping).

Files / Modules Affected

All six contracts; cross-cutting.

Dependencies

Issue #19, Issue #7.

Difficulty

Hard.

Estimated Effort

1 week.

Suggested Labels

reliability, storage, P2, long-term

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[malaysiaonelove]

Hi maintain,I will love to work on this issue,I have an experience and I have already reviewed the issue please assigned me to it and I will give a good result.

[Clement-coder]

Hi,

I’m a full-stack software and blockchain engineer with hands-on experience delivering production-ready solutions across frontend, backend, and blockchain systems.

I’d like to take ownership of this issue. I’ve reviewed the requirements and can implement a scalable, maintainable, and well-tested solution that fully satisfies the acceptance criteria.

Ready to start immediately and keep the team updated throughout the process.

[grantfox-oss]

🦊 GrantFox — @Clement-coder 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 #40)
2. Your PR will be reviewed by the Kqirox maintainers

Good luck! Track your progress on GrantFox.