Add tests proving admin can resolve disputes

[ositaemmanuel653-netizen]

Close #454

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• Add test_admin_resolve_dispute.rs with two new tests
• Admin resolves dispute with Release (vendor wins) and escrow transitions to Completed
• Admin resolves dispute with Refund (buyer wins) and escrow transitions to Refunded
• Verify correct payouts and arbitration fee handling in both scenarios
• Register new test module in lib.rs

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Summary

• Provide a clear and concise description of the changes.
• Link to any related issues using Fixes #issue or Related to #issue.

Testing

• All new code is covered by unit tests where applicable.
• Existing tests pass locally (cargo test).
• Added tests for edge cases and error conditions.
• Updated any integration tests if necessary.

Documentation

• Updated README.md if changes affect users.
• Updated docstrings/comments for new/modified functions.
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Code Quality

• Follows the project's coding style and conventions.
• No commented-out code or debug statements left in the codebase.
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• Code is properly formatted (cargo fmt).
• No new clippy warnings (cargo clippy).

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[ositaemmanuel653-netizen]

Close #454

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[JSE19]

CI/Test and CI/Check are failing, please cross check the failed checks and fix them

[JSE19]

👋 main has been fixed — \und_escrow\ and
aise_dispute\ are restored and clippy is clean. Could you rebase your branch on the latest main so CI re-runs? \git rebase main\ then force-push.

[ositaemmanuel653-netizen]

Done

[ositaemmanuel653-netizen]

Hello maintainer.check issue,dispute has been resolved.

[ositaemmanuel653-netizen]

Hello maintainer,please am still waiting for your final reviews as time is of the essence.

[ositaemmanuel653-netizen]

@JSE19 Please check and close.