Add negative zero offset parsing test

[johnpaulett]

Summary

• add equality helpers to _UTCOffset
• handle -0030 offsets correctly in parse_datetime
• test negative zero-hour timezone offset

Testing

• make lint
• make tests

---

https://chatgpt.com/codex/tasks/task_e_68461b29c16c832da5cc0d9c00f4b187

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.49%. Comparing base (0151932) to head (688e8b5).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #82      +/-   ##
==========================================
+ Coverage   90.38%   90.49%   +0.10%     
==========================================
  Files          20       20              
  Lines        1623     1641      +18     
  Branches      235      236       +1     
==========================================
+ Hits         1467     1485      +18     
  Misses        111      111              
  Partials       45       45              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.