feat(events): pipe displayTimezone through list and sidebar formatters

Sidebar (EventsMiniSidebar), public events list, member dashboard
"Upcoming" block, and EventTicketPurchase all formatted dates in
viewer-local TZ. Switch each formatter to accept the event (or an
eventTimezone prop) and pass it to Intl.DateTimeFormat so the
displayed wall-clock matches the event's intended zone.

app/pages/events/[slug].vue

@@ -131,6 +131,7 @@
           :event-id="event._id || event.id"
           :event-start-date="event.startDate"
           :event-title="event.title"
+          :event-timezone="eventTimeZone"
           :user-email="memberData?.email"
           :user-name="memberData?.name"
           @success="handleTicketSuccess"