feat: Refund eligibility and on-chain refund workflow for creators

[dotunv]

Overview

Add a refund-eligibility workflow that lets campaign creators (and admins) process partial or full on-chain refunds to contributors, with automatic campaign balance adjustment.

Motivation

Campaigns can fail, be cancelled, or creators may want to issue goodwill refunds. Today there's no structured refund path — creators have no way to return escrowed funds to a specific contributor through the UI, and the campaign/escrow bookkeeping isn't updated when refunds happen off-platform.

Proposed Design

1. Add a refunds table: contribution_id, campaign_id, amount, reason, status, processed_at, tx_hash
2. Add a creator view "Refunds" section listing contributions eligible for refund (status, amount, contributor)
3. Creator can initiate a partial or full refund on a contribution
4. Refunding submits an escrow return transaction on-chain returning funds to the contributor's wallet
5. On success, campaign raised_amount (and USD equivalent) decreases and the contribution is marked refunded
6. Refund requires confirmation with explicit amount and reason
7. Admin can force-refund and can add a note; refunds are logged in the audit trail
8. Contributor receives a notification and email when their contribution is refunded

Acceptance Criteria

• Creator can view list of eligible contributions for a campaign
• Creator can initiate partial or full refund with an amount and reason
• Refund submits a real escrow-return transaction on-chain
• Campaign raised_amount decreases on successful refund
• Contribution status is updated to refunded with original and refunded amounts
• Refund requires confirmation (no accidental double clicks)
• Admin can force-refund and leave an internal note
• Contributor gets a notification/email on refund
• Refund failure rolls back state and logs the error
• Tests cover: partial, full, failure rollback, admin force-refund, double-refund guard

[ojuotimi932]

@ojuotimi932 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi Maintainer Can I resolve this kindly assign

ℹ️ Repo Maintainers: To accept this application, review their application or assign @ojuotimi932 to this issue.

[Danitello123]

@Danitello123 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I’m a smart contract and full-stack developer who turns complex ideas into secure, production-ready blockchain code.
With strong skills in Rust and Solidity, I build systems that are fast, safe, and built to last.
My experience with the Stellar SDK lets me ship real-world Web3 solutions that actually move value

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Danitello123 to this issue.

[Noubata]

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

I can submit a PR within 1 hour. assign it to me

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

[Davoski1]

@Davoski1 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, please assign to me.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Davoski1 to this issue.

[drips-wave]

Congratulations, @DevALVIN-24! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @DevALVIN-24: 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 🌊