Event detail page formatted dates in viewer-local time, so a Lisbon
viewer of a Toronto ET event saw the time in WEST. Format with
event.displayTimezone instead so attendees see the event's intended
wall-clock + zone suffix ("6:00 AM EDT") regardless of where they sit.
useEventDateUtils.formatDate / formatTime / formatDateRange / isToday
now accept a { timeZone } option and pass it to Intl.DateTimeFormat.
Existing call sites that don't pass timeZone fall through to viewer-
local, matching prior behaviour.
