feat: min/max participants — shared ParticipantLimits component

- New ParticipantLimits component in FormField.tsx (reusable)
- Used in both Open Day settings and MC editor — identical layout
- Open Day: event-level min/max (DB migration 15)
- MC: per-event min/max (JSON fields)
- Public: waiting list when full, spots counter, amber success modal

src/app/admin/_components/FormField.tsx

@@ -11,6 +11,8 @@ interface InputFieldProps {
   type?: "text" | "url" | "tel";
 }
 
+const inputCls = "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";
+
 export function InputField({
   label,
   value,
@@ -26,12 +28,39 @@ export function InputField({
         value={value}
         onChange={(e) => onChange(e.target.value)}
         placeholder={placeholder}
-        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"
+        className={inputCls}
       />
     </div>
   );
 }
 
+export function ParticipantLimits({
+  min,
+  max,
+  onMinChange,
+  onMaxChange,
+}: {
+  min: number;
+  max: number;
+  onMinChange: (v: number) => void;
+  onMaxChange: (v: number) => void;
+}) {
+  return (
+    <div className="grid grid-cols-2 gap-3">
+      <div>
+        <label className="block text-sm text-neutral-400 mb-1.5">Мин. участников</label>
+        <input type="number" min={0} value={min} onChange={(e) => onMinChange(parseInt(e.target.value) || 0)} className={inputCls} />
+        <p className="text-[10px] text-neutral-600 mt-1">Если записей меньше — занятие можно отменить</p>
+      </div>
+      <div>
+        <label className="block text-sm text-neutral-400 mb-1.5">Макс. участников</label>
+        <input type="number" min={0} value={max} onChange={(e) => onMaxChange(parseInt(e.target.value) || 0)} className={inputCls} />
+        <p className="text-[10px] text-neutral-600 mt-1">0 = без лимита. При заполнении — лист ожидания</p>
+      </div>
+    </div>
+  );
+}
+
 interface TextareaFieldProps {
   label: string;
   value: string;