Complete back button logic for all admin pages in Telegram Mini App

Main sections navigate to /admin (15 pages)
Detail/edit pages navigate to parent lists (16 pages)
All pages use useBackButton hook with proper navigation paths
Native Telegram back button in Mini App, UI button on web
Email template pages keep UI-only back buttons as required

src/pages/AdminPromocodes.tsx

@@ -4,10 +4,23 @@ import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { useTranslation } from 'react-i18next';
 import i18n from '../i18n';
 import { promocodesApi, PromoCode, PromoCodeType } from '../api/promocodes';
-import { AdminBackButton } from '../components/admin';
+import { useBackButton } from '../platform/hooks/useBackButton';
+import { usePlatform } from '../platform/hooks/usePlatform';
 
 // Icons
 
+const BackIcon = () => (
+  <svg
+    className="h-5 w-5 text-dark-400"
+    fill="none"
+    viewBox="0 0 24 24"
+    stroke="currentColor"
+    strokeWidth={2}
+  >
+    <path strokeLinecap="round" strokeLinejoin="round" d="M15.75 19.5L8.25 12l7.5-7.5" />
+  </svg>
+);
+
 const PlusIcon = () => (
   <svg className="h-5 w-5" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={2}>
     <path strokeLinecap="round" strokeLinejoin="round" d="M12 4.5v15m7.5-7.5h-15" />
@@ -98,6 +111,10 @@ export default function AdminPromocodes() {
   const { t } = useTranslation();
   const navigate = useNavigate();
   const queryClient = useQueryClient();
+  const { capabilities } = usePlatform();
+
+  // Use native Telegram back button in Mini App
+  useBackButton(() => navigate('/admin'));
 
   const [deleteConfirm, setDeleteConfirm] = useState<number | null>(null);
   const [copiedCode, setCopiedCode] = useState<string | null>(null);
@@ -130,7 +147,15 @@ export default function AdminPromocodes() {
       {/* Header */}
       <div className="mb-6 flex flex-col gap-4 sm:flex-row sm:items-center sm:justify-between">
         <div className="flex items-center gap-3">
-          <AdminBackButton />
+          {/* Show back button only on web, not in Telegram Mini App */}
+          {!capabilities.hasBackButton && (
+            <button
+              onClick={() => navigate('/admin')}
+              className="flex h-10 w-10 items-center justify-center rounded-xl border border-dark-700 bg-dark-800 transition-colors hover:border-dark-600"
+            >
+              <BackIcon />
+            </button>
+          )}
           <div>
             <h1 className="text-xl font-semibold text-dark-100">{t('admin.promocodes.title')}</h1>
             <p className="text-sm text-dark-400">{t('admin.promocodes.subtitle')}</p>