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/member/dashboard.vue

@@ -60,9 +60,7 @@
                   :to="`/events/${evt.slug || evt._id}`"
                   class="event-item"
                 >
-                  <span class="event-date">{{
-                    formatEventDate(evt.startDate)
-                  }}</span>
+                  <span class="event-date">{{ formatEventDate(evt) }}</span>
                   <span class="event-title">{{ evt.title }}</span>
                   <CircleBadge v-if="evt.circle" :circle="evt.circle" />
                 </NuxtLink>
@@ -365,20 +363,22 @@ const getEventImageUrl = (featureImage) => {
   return "";
 };
 
-const formatEventDate = (dateString) => {
-  const date = new Date(dateString);
+const formatEventDate = (event) => {
+  if (!event?.startDate) return "";
   return new Intl.DateTimeFormat("en-US", {
     month: "short",
     day: "numeric",
-  }).format(date);
+    timeZone: event.displayTimezone || "America/Toronto",
+  }).format(new Date(event.startDate));
 };
 
-const formatEventTime = (dateString) => {
-  const date = new Date(dateString);
+const formatEventTime = (event) => {
+  if (!event?.startDate) return "";
   return new Intl.DateTimeFormat("en-US", {
     hour: "numeric",
     minute: "2-digit",
-  }).format(date);
+    timeZone: event.displayTimezone || "America/Toronto",
+  }).format(new Date(event.startDate));
 };
 
 const formatMemberSince = (dateString) => {