fix(payment-methods): admin display_name/description override locale on balance

White-label (per-method display_name + description in admin) was defeated on
balance/top-up pages: render used `translatedName || method.name` and
`translatedDesc || method.description`, so the bundled locale always won and
the admin override was ignored.

- Flip priority: admin-configured value first, locale as fallback
  (TopUpMethodSelect, Balance)
- Add missing Description field to payment-method edit page
  (mirrors Display name: description / reset_description)
- Add description to admin PaymentMethodConfig type
- Add description/descriptionHint i18n keys (ru, en)

src/pages/AdminPaymentMethodEdit.tsx

@@ -232,6 +232,7 @@ export default function AdminPaymentMethodEdit() {
   // Local state for editing
   const [isEnabled, setIsEnabled] = useState(false);
   const [customName, setCustomName] = useState('');
+  const [customDesc, setCustomDesc] = useState('');
   const [subOptions, setSubOptions] = useState<Record<string, boolean>>({});
   const [minAmount, setMinAmount] = useState<number | ''>('');
   const [maxAmount, setMaxAmount] = useState<number | ''>('');
@@ -249,6 +250,7 @@ export default function AdminPaymentMethodEdit() {
     if (config) {
       setIsEnabled(config.is_enabled);
       setCustomName(config.display_name || '');
+      setCustomDesc(config.description || '');
       setSubOptions(config.sub_options || {});
       setMinAmount(config.min_amount_kopeks ?? '');
       setMaxAmount(config.max_amount_kopeks ?? '');
@@ -290,6 +292,13 @@ export default function AdminPaymentMethodEdit() {
       data.reset_display_name = true;
     }
 
+    // Description
+    if (customDesc.trim()) {
+      data.description = customDesc.trim();
+    } else {
+      data.reset_description = true;
+    }
+
     // Sub-options
     if (config.available_sub_options) {
       data.sub_options = subOptions;
@@ -478,6 +487,22 @@ export default function AdminPaymentMethodEdit() {
           </p>
         </div>
 
+        {/* Description */}
+        <div>
+          <label className="mb-2 block text-sm font-medium text-dark-300">
+            {t('admin.paymentMethods.description')}
+          </label>
+          <textarea
+            value={customDesc}
+            onChange={(e) => setCustomDesc(e.target.value)}
+            rows={2}
+            className="input"
+          />
+          <p className="mt-1 text-xs text-dark-500">
+            {t('admin.paymentMethods.descriptionHint')}
+          </p>
+        </div>
+
         {/* Sub-options */}
         {config.available_sub_options && config.available_sub_options.length > 0 && (
           <div>