Test: Implement Unit: CSV Parser & Data Validation for Bulk Shipments

[EzeanoroEbuka]

Closes #469

Summary
Implemented unit tests for the bulk shipment CSV parser and data validation utility. The tests ensure that valid uploads are mapped accurately to typed objects and that malformed rows generate structured, actionable errors for the user interface.

Changes Proposed

• Added __tests__/lib/csvParser.test.ts to cover the CSV parsing logic.
• Added happy path tests for correctly formatted CSV strings, verifying object mapping and type coercion.
• Implemented edge case tests for trailing whitespace and empty rows.
• Added error handling assertions for missing fields (recipient, amount, currency) and invalid numeric formats (NaN, negative amounts, zero).
• Verified the parser's ability to handle mixed successful and failed rows within the same file (partial success).

Acceptance Criteria Checklist

• Forked the repository and created a new branch using the designated branch name.
• Wrote the required tests using Jest.
• Mocked external dependencies to prevent flaky tests.
• Ensured the new tests pass reliably and meet code coverage standards.
• Ran the full test suite locally to verify no existing tests are broken.

How to Test
Run the Jest test suite locally to verify the parser validation:
```bash
npm run test
```

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