* fix: handle invalid timezones gracefully in getLuckyUser
Co-Authored-By: benny@cal.com <sldisek783@gmail.com>
* refactor: move timezone validation to getCalendarsEvents with offset conversion
- Move invalid timezone handling from getLuckyUser.ts to getCalendarsEvents.ts
- Add convertOffsetToEtcGmt() to convert offset formats (GMT-05:00, UTC+08:00) to valid IANA Etc/GMT timezones
- Preserves timezone precision for fairness calculations instead of falling back to UTC
- Add unit tests for timezone conversion scenarios
* refactor: extract timezone conversion to dedicated file
- Create timezone-conversion.ts with concise convertOffsetToIanaTimezone and normalizeTimezone functions
- Update getCalendarsEvents.ts to import from the new file
- Follow kebab-case naming convention for utility files
* test: add unit tests for timezone conversion proving Intl.DateTimeFormat behavior
- Add tests proving Intl.DateTimeFormat throws RangeError for offset formats (GMT-05:00, UTC+08:00)
- Add tests for convertOffsetToIanaTimezone function
- Add tests for normalizeTimezone function
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Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
