[Contract] In-memory Buffer for Payout Queue (Anti-Congestion)

[gabito1451]

Independence Note: Provide entirely empty stub structs representing interacting Protocols without network hooks.

Context:
Executing dozens of payouts in a single transaction can exceed gas limits. We need a way to queue payouts natively and process them in chunks.

Objective:
Create an internal state to buffer pending payouts.

Acceptance Criteria:

• Define a PayoutQueue struct using storage().persistent().
• Add a method add_payout(recipient, amount) that appends to an internal vector.
• Implement process_payout_batch(count) which pops the first count items and performs the transfers.
• Add tests showing that items are added and removed in the correct FIFO order.

Technical Pointers:

• Using a vector in persistent storage has gas implications; ensure the count is limited per call to stay within limits.

[AlienScroll78]

@AlienScroll78 has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Dear Maintainer i would love to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @AlienScroll78 to this issue.

[oscar24357]

@oscar24357 has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Hi maintainer, i would love to work on this issue, pls assign me, thank you

ℹ️ Repo Maintainers: To accept this application, review their application or assign @oscar24357 to this issue.

[GEEKYFOCUS]

@GEEKYFOCUS has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Hello Maintainer. I've reviewed the application thoroughly and i fully understand. Haven't resolved in issues in wave 3 with great feedbacks, I can work on this. Please assign me the issue

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

[drips-wave]

Congratulations, @oscar24357! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

🧑‍💻 @oscar24357: 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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[drips-wave]

This issue has been marked as completed by a Drips Wave moderator for @oscar24357 as part of the Stellar Wave Program's 4th Wave 🥳

Moderator's reason: [Auto-assessed] The contributor successfully implemented the PayoutQueue as requested, including the persistent storage handling, FIFO logic, and the specific stub protocol required by the issue. The PR includes comprehensive tests for batch processing and FIFO order, and no maintainer objections have been raised.

😎 @oscar24357: 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.