feat: discount toggle flag, hide price from success popup

- Admin: "Добавить скидку" toggle — OFF hides discount fields and sets to 0
- Public: discount line hidden when discountPrice=0
- Success popup: removed price/booking count info

src/components/ui/SignupModal.tsx

@@ -178,13 +178,6 @@ export function SignupModal({
                   {successMessage || "Вы записаны!"}
                 </h3>
                 {subtitle && <p className="mt-1 text-sm text-neutral-400">{subtitle}</p>}
-                {successData?.totalBookings !== undefined && (
-                  <p className="mt-3 text-sm text-white">
-                    Вы записаны на <span className="text-gold font-semibold">{String(successData.totalBookings)}</span> занятий.
-                    <br />
-                    Стоимость: <span className="text-gold font-semibold">{String(successData.pricePerClass)} BYN</span> за занятие
-                  </p>
-                )}
               </>
             )}
             <button