fix(attendance_request): enhance leave record checks for half-day attendance requests (backport #4549)

[mergify]

Fixes #4531
Changes:

• fixed status change for a day which has half-day leave, and the other half is being marked as absent due to auto attendance.
• It did not let us add an attendance request for the above condition.

Screen.Recording.2026-05-19.at.1.34.19.PM.mov

Summary by CodeRabbit

• Bug Fixes

  • Improved half-day attendance request handling: absent half-days can now be updated to present and avoid incorrect "unchanged" skips
  • Tightened leave validation to accurately detect approved leave spanning attendance dates, including half-day considerations
  • Better behavior when shift auto-attendance is enabled for missing check-ins

• Tests

  • Added tests covering half-day absent→present updates and shift auto-attendance half-day scenarios

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This is an automatic backport of pull request #4549 done by [Mergify](https://mergify.com).