feat: Add replay protection for contributions

[cypriannwokolo2-creator]

Description

Double-spend risk exists if contributions are not unique per round. Add replay protection.

Requirements

• Track contribution uniqueness per round per member
• Reject duplicate contributions
• Add tests for replay scenarios

Acceptance Criteria

• Each contribution is unique per round
• Duplicate contributions rejected
• Tests verify replay protection

Priority

High

[Emoji-dot]

@Emoji-dot 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

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[classicjoshua1-creator]

@classicjoshua1-creator has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi Maintainer, I believe this task is within my capabilities and I’d be happy to work on resolving it. Please consider assigning it to me.

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[Peolite001]

@Peolite001 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I would love to work on this issue

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[webdevayo]

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

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[Keengfk]

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

i would love to work on this issue and summit a clean pr withing 1 days

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[Komelove]

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

I’d be happy to take this issue. I’ve looked through the requirements and have a plan for approaching the implementation. I’ll investigate the existing code and dependencies, make the required changes, verify the behaviour with tests, and provide a concise PR explaining what was changed. I can start immediately and will communicate any blockers during development.

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[LiegeFx]

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

Hello maintainer, I would love to work on this issue, kindly assign it to me

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[abdulrcrtw]

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

Hi there, I'd like to contribute to this.

I'll treat this as security-sensitive: careful implementation, no logging of sensitive values, and coverage for the edge cases called out.

Planned approach, based on the acceptance criteria:

• Each contribution is unique per round
• Duplicate contributions rejected
• Tests verify replay protection

Happy to get started right away if assigned — looking forward to contributing.

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

[PEPPERITO23]

@PEPPERITO23 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I've reviewed the issue thoroughly and can start working on it right away. Looking forward to contributing

ℹ️ Repo Maintainers: To accept this application, review their application or assign @PEPPERITO23 to this issue.

[drips-wave]

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

🧑‍💻 @abdulrcrtw: 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 🌊