PYSEC-2026-2722 Open WebUI IDOR: Calendar event re-parenting allows writing events into another user's calendar

Summary POST /api/v1/calendars/events/eventid/update validates that the caller has write access to the calendar the event currently belongs to, but does not validate the destination calendarid supplied in the request body. The model layer then persists the new calendarid unconditionally. A regula...