Add batch-settlement bundling with up to 64 entries per ledger

[greatest0fallt1me]

Description

This is a smart-contract issue for the GrantFox campaign. Allow settlement.batch_settle to process up to 64 settlements per call to reduce ledger churn under load.

Requirements and Context

• Max batch = 64
• Partial success allowed
• Returns array of outcomes
• Gas-profiled at cap
• Must be secure, tested, and documented
• Should be efficient and easy to review

Suggested Execution

1. Fork the repo and create a branch

   git checkout -b feature/batch-settle

2. Implement changes
   • contracts/settlement/src/lib.rs
   • contracts/settlement/src/batch.rs (new)
3. Test and commit
   • Run the repo's standard test suite and lint
   • Cover edge cases; include output in the PR

Example commit message

feat: batch_settle up to 64 entries

Acceptance Criteria

• Cap enforced
• Partial success returned
• Gas under budget
• Tests cover cap

Guidelines

• Minimum 95% test coverage with cargo test
• require_auth on every state-changing entrypoint
• Overflow-safe math; no unwrap() in production paths
• Clear NatSpec-style /// rustdoc
• Timeframe: 96 hours

[obswrld]

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

I would like to work on this

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

[Truphile]

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

Hi team, I’d love to be assigned to this issue.
​As a returning contributor, I’m already well-acquainted with the project’s architectural boundaries, conventions, and CI/CD workflow. Having implemented very similar patterns in production before, I can deliver a clean, highly isolated solution that requires minimal review overhead and eliminates risk of architectural drift.
​I’ve reviewed the acceptance criteria and am ready to open a targeted PR as soon as it's assigned. Thanks!

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

[drips-wave]

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

🧑‍💻 @Truphile: 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.

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