[BE-052] Sweep: Concurrent candidate processing

[ONEONUORA]

Description\nProcess auto-sweep actions concurrently rather than sequentially.\n\n## Files to Edit/Create\n- backend/src/services/sweep_worker.rs\n\n## Acceptance Criteria\n- Spawn tokio tasks to execute sweeps in parallel.\n\n## Guidance / Hints\nUse join_all and limit concurrency rates.

[Andreschuks101]

@Andreschuks101 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I would love to resolve this issue, please assign it to me

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Congratulations, @Andreschuks101! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

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[alade-dev]

@alade-dev has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi, I would love to work on this issue.

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[TechBroAfrica]

@TechBroAfrica has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I aim to be the kind of contributor maintainers can rely on. Whether it's fixing bugs, implementing features, or improving documentation, I prioritize understanding project standards, communicating clearly, and delivering high-quality work. I believe successful open-source contributions are built on consistency, accountability, and respect for the project's long-term vision.

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

🧑‍💻 @TechBroAfrica: 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

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🤠 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.

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