Bug Description

When creating calendar events with timezone-aware timestamps, the time is incorrectly interpreted.

Steps to Reproduce

1. Run: gog calendar create primary --summary "会议" --from 2026-03-06T19:00:00+08:00 --to 2026-03-06T20:00:00+08:00 --force
2. Check the created event time

Expected Behavior

• Input: 2026-03-06T19:00:00+08:00 (19:00 Beijing Time)
• Should create event at 19:00 Beijing / 11:00 UTC

Actual Behavior

• Event created at 06:00 local time (shows as 06:00 America/New_York or UTC-5)
• The timezone in +08:00 is ignored, defaults to UTC-5

Environment

• gog version: v0.11.0
• OS: macOS
• Calendar: Google Calendar (primary)

Additional Notes

• Using RFC3339 format with timezone (e.g., +08:00) does not work
• The tool seems to default to America/New_York or UTC-5 timezone regardless of input