feat: mobile UX, admin polish, rate limiting, and media assets

- Mobile responsiveness improvements across admin and public sections
- Admin: bookings modal, open-day page, team page, layout polish
- Added rate limiting, CSRF hardening, auth-edge improvements
- Scroll reveal, floating contact, back-to-top, Yandex map fixes
- Schedule filters refactor, team profile/info component updates
- New useTrainerPhotos hook
- Added class, team, master-class, and news images

src/app/admin/page.tsx

@@ -91,9 +91,9 @@ export default function AdminDashboard() {
 
   useEffect(() => {
     adminFetch("/api/admin/unread-counts")
-      .then((r) => r.json())
+      .then((r) => { if (!r.ok) throw new Error(); return r.json(); })
       .then((data: UnreadCounts) => setCounts(data))
-      .catch(() => {});
+      .catch(() => { /* initial load — non-critical */ });
   }, []);
 
   return (