Mobile-friendly admin pages, redesigned homepage Next Event card

- Extract shared mobile components (BottomSheet, MoreMenu, Dropdown, etc.) into MobileComponents.tsx
- Make admin pages mobile-friendly: bookings, emails, events, faq, payments, tickets, users
- Redesign homepage Next Event card with banner image, responsive layout, and updated styling
- Fix past events showing on homepage/linktree: use proper Date comparison, auto-unfeature expired events
- Add "Over" tag to admin events list for past events
- Fix backend FRONTEND_URL for cache revalidation

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/app/linktree/page.tsx

@@ -24,7 +24,16 @@ export default function LinktreePage() {
 
   useEffect(() => {
     eventsApi.getNextUpcoming()
-      .then(({ event }) => setNextEvent(event))
+      .then(({ event }) => {
+        if (event) {
+          const endTime = event.endDatetime || event.startDatetime;
+          if (new Date(endTime).getTime() <= Date.now()) {
+            setNextEvent(null);
+            return;
+          }
+        }
+        setNextEvent(event);
+      })
       .catch(console.error)
       .finally(() => setLoading(false));
   }, []);