Fix back button cycling in Telegram Mini App

Add replace: true to all navigate() calls in useBackButton hooks
Prevents history cycles when navigating back and forth
All 32 admin pages now use navigate(path, { replace: true })
Back button now goes directly to parent without cycling

src/pages/AdminPromocodeCreate.tsx

@@ -51,7 +51,7 @@ export default function AdminPromocodeCreate() {
   const isEdit = !!id;
 
   // Use native Telegram back button in Mini App
-  useBackButton(() => navigate('/admin/promocodes'));
+  useBackButton(() => navigate('/admin/promocodes', { replace: true }));
 
   // Form state
   const [code, setCode] = useState('');