Add a settle-confirmation worker that re-checks tx finality before marking claim done

[greatest0fallt1me]

Description

This is a backend issue for the GrantFox campaign. Worker requeries Horizon for each pending claim's tx until finality before marking the claim status as settled.

Requirements and Context

• Reads from claims table
• Backoff schedule
• Marks settled on finality
• Tests cover
• 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 task/settle-confirmer

2. Implement changes
   • src/workers/settleConfirmer.ts (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: claim finality confirmer worker

Acceptance Criteria

• Polls correctly
• Backoff sane
• Settle marked
• Tests pass

Guidelines

• Minimum 90% test coverage on changed lines
• Input validation at the boundary; standardized error envelope
• Structured logging with correlation IDs
• Clear documentation and inline comments
• Timeframe: 96 hours

[adeboladee]

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

Hello maintainer, Please I would like to work on this issue

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