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/layout.tsx

@@ -56,17 +56,19 @@ export default function AdminLayout({
   const [unreadTotal, setUnreadTotal] = useState(0);
   const isLoginPage = pathname === "/admin/login";
 
-  // Fetch unread counts — poll every 10s
+  // Fetch unread counts — poll every 10s, stop after 3 consecutive failures
   useEffect(() => {
     if (isLoginPage) return;
+    let failures = 0;
+    let interval: ReturnType<typeof setInterval>;
     function fetchCounts() {
       adminFetch("/api/admin/unread-counts")
-        .then((r) => r.json())
-        .then((data: { total: number }) => setUnreadTotal(data.total))
-        .catch(() => {});
+        .then((r) => { if (!r.ok) throw new Error(); return r.json(); })
+        .then((data: { total: number }) => { setUnreadTotal(data.total); failures = 0; })
+        .catch(() => { failures++; if (failures >= 3 && interval) clearInterval(interval); });
     }
     fetchCounts();
-    const interval = setInterval(fetchCounts, 10000);
+    interval = setInterval(fetchCounts, 10000);
     return () => clearInterval(interval);
   }, [isLoginPage]);