perf: Implement storage cleanup for expired and completed escrows

[nanaf6203-bit]

Description

Escrow data (documents, conditions, signatures, audit logs) persists indefinitely after completion, bloating on-chain storage. Implement cleanup mechanism.

Acceptance Criteria

• Add cleanup_escrow(escrow_id) message (any participant or admin after completion)
• Remove documents, conditions, signatures for completed/released/refunded escrows
• Preserve minimal EscrowSummary: id, property_id, buyer, seller, amount, status, completed_at
• Keep audit trail for compliance but move to compressed format
• Emit EscrowCleanedUp event
• Add get_escrow_summary(escrow_id) query for cleaned-up escrows
• Test: cleanup removes detailed data but preserves summary
• Test: cannot cleanup active escrow
• Measure storage savings for typical escrow lifecycle

[drips-wave]

Congratulations, @tecmalik! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @tecmalik: 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.

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[Nabeelahh]

@Nabeelahh has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer I have thoroughly read the description to this issue and I can resolve this according to the description required ensuring it meet all the acceptance criteria kindly assign..

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

[Pilot39]

@Pilot39 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I would like to work on this issue, kindly assign me

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Pilot39 to this issue.

[drips-wave]

Congratulations, @Nabeelahh! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Nabeelahh: 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

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊