List calendar events (v2)

External calendar events fetched live from the authenticated user's connected Google / Office365 credentials via the sync-engine — there's no DB table. Optional limit and dateRange.{start,end} (ISO datetimes) scope the window; optional searchQuery free-text-filters by title, description, location, and attendees. Returns { data: { calendar_events, pagination } }; an empty list when no calendar is connected.