refactor: show event slug after name in header

Display the event slug in small muted text directly after the event
name in the EventTabsNav header.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/app/src/components/events/EventTabsNav.vue

@@ -249,6 +249,7 @@ const backRoute = computed(() => {
                   <span class="text-medium-emphasis mx-1">&raquo;</span>
                 </template>
                 {{ event.name }}
+                <span class="text-body-2 text-medium-emphasis font-weight-regular ms-2">{{ event.slug }}</span>
               </h4>
               <VChip
                 v-if="event.event_type === 'festival' || event.event_type === 'series'"