feat: multi-popular toggle for pricing, BYN price field for master classes

- Replace single popular dropdown with per-item toggle switch in pricing admin
- Add PriceField component to master classes admin (strips/adds BYN suffix)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/admin/master-classes/page.tsx

@@ -7,6 +7,30 @@ import { ArrayEditor } from "../_components/ArrayEditor";
 import { Plus, X, Upload, Loader2, ImageIcon, AlertCircle, Check, ChevronDown, ChevronUp, Instagram, Send, Trash2, Pencil } from "lucide-react";
 import type { MasterClassItem, MasterClassSlot } from "@/types/content";
 
+function PriceField({ label, value, onChange, placeholder }: { label: string; value: string; onChange: (v: string) => void; placeholder?: string }) {
+  const raw = value.replace(/\s*BYN\s*$/i, "").trim();
+  return (
+    <div>
+      <label className="block text-sm text-neutral-400 mb-1.5">{label}</label>
+      <div className="flex rounded-lg border border-white/10 bg-neutral-800 focus-within:border-gold transition-colors">
+        <input
+          type="text"
+          value={raw}
+          onChange={(e) => {
+            const v = e.target.value;
+            onChange(v ? `${v} BYN` : "");
+          }}
+          placeholder={placeholder ?? "0"}
+          className="flex-1 bg-transparent px-4 py-2.5 text-white placeholder-neutral-500 outline-none min-w-0"
+        />
+        <span className="flex items-center pr-4 text-sm font-medium text-gold select-none">
+          BYN
+        </span>
+      </div>
+    </div>
+  );
+}
+
 interface MasterClassesData {
   title: string;
   successMessage?: string;
@@ -888,11 +912,11 @@ export default function MasterClassesEditorPage() {
                   />
                 </div>
 
-                <InputField
+                <PriceField
                   label="Стоимость"
                   value={item.cost}
                   onChange={(v) => updateItem({ ...item, cost: v })}
-                  placeholder="40 BYN"
+                  placeholder="40"
                 />
 
                 {locations.length > 0 && (