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* fix(caldav): use consistent UIDs and inject VTIMEZONE in iCalendar output Two remaining CalDAV interop issues from #9485: 1. UID consistency: use the booking's canonical UID (event.uid) instead of always generating a new random UUID. CalDAV servers use UID as the event identifier — different UIDs cause duplicate calendar entries. 2. VTIMEZONE injection: the ics library generates UTC times with no VTIMEZONE block. CalDAV servers like Fastmail read this as UTC and send scheduling emails with wrong times. Per RFC 5545 §3.6.5, DTSTART with TZID requires a matching VTIMEZONE component. We now build a proper VTIMEZONE using binary-searched DST transitions for the event's year, handling Northern/Southern hemisphere correctly. * fix: use pre-transition offset for VTIMEZONE DTSTART per RFC 5545 The DTSTART in VTIMEZONE components must represent the local time interpreted with the pre-transition offset (TZOFFSETFROM), not the post-transition offset. For example, US Eastern spring forward DTSTART should be 02:00 (EST), not 03:00 (EDT). * Remove comments on UID handling in createEvent Removed comments about UID handling for calendar events. * Revise injectVTimezone documentation Update injectVTimezone function documentation to clarify UTC handling. --------- Co-authored-by: Anik Dhabal Babu <81948346+anikdhabal@users.noreply.github.com>