…NewTimeSlot reschedule call

CI-002 gap closure: When owner reschedules a seated booking to a new time slot,
EventManager.reschedule() was called without bufferContext (8th argument), causing
orphaned buffer events in external calendars when syncBuffersToCalendar is enabled.

Changes:
- Import BufferEventContext type from EventManager
- Build buffer context from eventType and organizerUser data when
  syncBuffersToCalendar is truthy (matching RegularBookingService pattern)
- Pass bufferCtx as 8th argument to eventManager.reschedule() to enable
  buffer event delete-and-recreate lifecycle on seated booking reschedule

When syncBuffersToCalendar is falsy/null/undefined, bufferCtx is undefined
and no buffer operations occur (zero regression to existing flows).

…eeDeleteBooking

CI-002 gap closure: When the last attendee leaves a seated booking,
the reference cleanup loop now handles buffer_time_before and
buffer_time_after references in addition to _video and _calendar types.

Previously, buffer event references were silently skipped because the
loop only checked for _video and _calendar type patterns. This left
orphaned buffer events in external calendars when syncBuffersToCalendar
was enabled and the calendar-buffer-sync feature flag was active.

The fix adds a new conditional block after the _calendar handling that:
- Matches references with type.startsWith('buffer_time')
- Guards with originalBookingEvt (same as _calendar block)
- Uses getCalendar(credential, 'booking') to obtain the adapter
- Calls calendar.deleteEvent() to remove the external calendar event
- Pushes the deletion promise to integrationsToDelete for batch execution

The fix is a no-op when:
- syncBuffersToCalendar is false (no buffer references exist)
- calendar-buffer-sync flag is disabled (no buffer references created)
- originalBookingEvt is undefined (guard prevents execution)

…dBookings buffer cleanup

- Extract buffer cleanup logic into dedicated deleteBufferEventsForCancelledBooking() helper
  to bring combineTwoSeatedBookings under Biome noExcessiveLinesPerFunction threshold (INFO)
- Move prisma.bookingReference.update soft-delete outside if(ref.uid) guard to match
  EventManager.ts:1610-1614 reference pattern — ensures references without UIDs are
  still soft-deleted defensively (MINOR)

Both changes follow the CI-002 gap closure patterns established in EventManager.ts.

…re in seated bookings

Add comprehensive test coverage for buffer event lifecycle management in
seated booking flows, verifying the three CI-002 gap closure bug fixes:

Bug 1 - moveSeatedBookingToNewTimeSlot: Verify bufferContext is passed as
8th argument to eventManager.reschedule() when syncBuffersToCalendar=true,
and is undefined when syncBuffersToCalendar=false.

Bug 2 - combineTwoSeatedBookings: Verify source booking buffer events are
cleaned up after merge cancellation, and that no duplicate buffer events
are created on the target booking (8th arg to reschedule is undefined).

Bug 3 - lastAttendeeDeleteBooking: Verify buffer_time_before and
buffer_time_after references are processed in the cleanup loop and
calendar.deleteEvent() is called for each, and that no buffer-related
deleteEvent calls occur when no buffer references exist.

All 6 new tests pass alongside the existing 20 seated booking tests.
No existing tests or assertions were modified.

…gap closure

- Test 3 (merge flow): Replace vacuous toBeGreaterThanOrEqual(0) with
  calendar mock setup and UID presence assertions verifying both
  buffer-before-uid and buffer-after-uid are deleted (MAJOR finding)
- Test 5 (last attendee): Replace weak toBeGreaterThanOrEqual(1) with
  toBeGreaterThanOrEqual(2) and individual UID presence checks (MINOR)
- Add new test: verify merge flow skips buffer cleanup when
  calendar-buffer-sync feature flag is disabled (INFO finding)

All 27 seated booking tests pass. Zero new compilation errors,
zero new lint violations, zero regressions.

…n updateEvent result for buffer event creation on reschedule (CI-002 gap)

Root cause: CalendarManager.updateEvent() did not return credentialId,
delegatedToId, or externalId in its EventResult, while createEvent() did.
This caused EventManager.createBufferEventsForBooking() to fail credential
resolution during non-seated booking reschedule, silently skipping buffer
event creation at the rescheduled time.

Fix: Add the three missing fields to updateEvent's return object, matching
createEvent's return shape. This enables the buffer event credential lookup
in EventManager to succeed after an updateAllCalendarEvents() call.

Tests: 7 new test cases in CalendarManager.test.ts verify updateEvent now
returns credentialId, delegatedToId, and externalId in all scenarios
(success, failure, delegation, null externalCalendarId).

…nd cancellation

Root cause: BaseCalendarService.deleteEvent() used string concatenation for
CalDAV object URL construction (`${cal.externalId}${uid}.ics`), which fails
when the calendar URL lacks a trailing slash. tsdav's createCalendarObject uses
`new URL(filename, calendar.url).href` which correctly resolves relative URLs.

Fix 1: Update getEventsByUID() to use `new URL(`${uid}.ics`, calendarUrl)`
for consistent URL construction matching tsdav's creation path.

Fix 2: Accept optional externalCalendarId in deleteEvent() for direct CalDAV
object URL construction. Buffer events store externalCalendarId in
BookingReference, enabling direct deletion without expensive listCalendars().

Falls back to full calendar search when direct lookup returns empty.

Includes 5 new test cases covering:
- Direct buffer event deletion via externalCalendarId
- Fallback to full calendar search
- URL construction for calendar URLs without trailing slash
- Buffer event deletion on reschedule (before + after events)
- Buffer event deletion on cancellation (last attendee leaves)