🧪 test: add coverage for parseCafefDate

[toreleon]

🎯 What: Added comprehensive unit tests for parseCafefDate in src/data/sources/cafef.ts to improve test coverage and safeguard date-parsing logic.
📊 Coverage: Covered all logical paths: falsy inputs, Microsoft JSON date format, valid standard/ISO dates, invalid date strings, and already ISO-like strings.
✨ Result: Improved robustness of CafeF data parsing by validating date transformations systematically.

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PR created automatically by Jules for task 11495911604662027448 started by @toreleon

[google-labs-jules]

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