fix: handle UTC offset timezones

[SebastianKrupinski]

Summary

• added logic to handle UTC offset timezones properly "DTSTART;TZID="UTC-04:00":20260728T111500"

[pi0n00r]

Thanks for moving this into the shared timezone parser. This covers the original UTC-04:00 case (and the compact UTC-0400 form) at the correct layer, so it is preferable to retaining a Calendar Dashboard-only correction.

The current CI failures appear limited to the two new PHPUnit data providers: PHPUnit 11 requires them to be static, and Rector expects #[DataProvider(...)] attributes rather than @dataProvider annotations. Once that is green, we can validate the dependency through Nextcloud and retire the application-local patch when the fixed vobject release is consumed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.66%. Comparing base (0ab3690) to head (e4407cb).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #790   +/-   ##
=========================================
  Coverage     98.66%   98.66%           
- Complexity     1748     1757    +9     
=========================================
  Files            71       71           
  Lines          5154     5165   +11     
=========================================
+ Hits           5085     5096   +11     
  Misses           69       69           

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[pi0n00r]

Confirmed: the corrected head is green across PHP 8.2 through 8.5, including Rector and the fixed-offset regression. Thanks for turning this around so quickly.