When creating a recurring event using --rrule, the API returns 'Missing time zone definition for start time', even though the --from and --to times include +TZ offset.

Steps to reproduce:

1. Authenticate with Google Calendar.
2. Run: gog calendar create --summary 'Test' --from '2026-03-03T20:00:00+01:00' --to '2026-03-03T20:30:00+01:00' --rrule 'RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR'
3. Error: Google API error (400 required): Missing time zone definition for start time.

Expected: Event created with recurrence.
Actual: Error due to missing timeZone in start object for recurring events.

Single events work fine with TZ. Update with --rrule also fails with 'Invalid recurrence rule'.

Version: v0.9.0 (99d9575)
OS: macOS