test: add comprehensive edge-case unit tests for jira-utils

[bhavyanjain3004]

Description

This PR adds comprehensive edge-case unit test coverage for the jira-utils module to verify Jira integration utilities.

Changes

• Added tests to check case-sensitivity and whitespace handling for statusCategory in categorizeStatus().
• Added tests for calculateMetrics() to verify zero-duration intervals (where resolved and created times are equal), negative durations (resolved before created), and invalid date strings (which produce NaN).

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GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

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• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

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• quality:clean — ×1.2 multiplier
• quality:exceptional — ×1.5 multiplier

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Type labels (type:*) are auto-detected from files and title. Review and adjust if needed.
Points formula: (difficulty × quality_multiplier) + type_bonus