feat: admin-editable success + waiting list messages for MC and Open Day

src/app/admin/open-day/page.tsx

@@ -19,6 +19,8 @@ interface OpenDayEvent {
   discountThreshold: number;
   minBookings: number;
   maxParticipants: number;
+  successMessage?: string;
+  waitingListText?: string;
   active: boolean;
 }
 
@@ -100,6 +102,29 @@ function EventSettings({
         />
       </div>
 
+      <div className="grid gap-4 sm:grid-cols-2">
+        <div>
+          <label className="block text-sm text-neutral-400 mb-1.5">Текст после записи</label>
+          <textarea
+            value={event.successMessage || ""}
+            onChange={(e) => onChange({ successMessage: e.target.value || undefined })}
+            rows={2}
+            className="w-full rounded-lg border border-white/10 bg-neutral-800 px-4 py-2.5 text-white placeholder-neutral-500 outline-none focus:border-gold transition-colors resize-none"
+            placeholder="Вы записаны!"
+          />
+        </div>
+        <div>
+          <label className="block text-sm text-neutral-400 mb-1.5">Текст для листа ожидания</label>
+          <textarea
+            value={event.waitingListText || ""}
+            onChange={(e) => onChange({ waitingListText: e.target.value || undefined })}
+            rows={2}
+            className="w-full rounded-lg border border-white/10 bg-neutral-800 px-4 py-2.5 text-white placeholder-neutral-500 outline-none focus:border-gold transition-colors resize-none"
+            placeholder="Все места заняты, но мы добавили вас в лист ожидания..."
+          />
+        </div>
+      </div>
+
       <div>
         <label className="block text-sm text-neutral-400 mb-1.5">Цена за занятие (BYN)</label>
         <input