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/AdminTariffs.tsx

@@ -2,8 +2,9 @@ import { useNavigate } from 'react-router-dom';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { useTranslation } from 'react-i18next';
 import { tariffsApi, TariffListItem } from '../api/tariffs';
-import { AdminBackButton } from '../components/admin';
 import { useDestructiveConfirm, useNotify } from '@/platform';
+import { useBackButton } from '../platform/hooks/useBackButton';
+import { usePlatform } from '../platform/hooks/usePlatform';
 
 // Icons
 const PlusIcon = () => (
@@ -54,12 +55,29 @@ const GiftIcon = () => (
   </svg>
 );
 
+// BackIcon
+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>
+);
+
 export default function AdminTariffs() {
   const { t } = useTranslation();
   const navigate = useNavigate();
   const queryClient = useQueryClient();
   const confirmDelete = useDestructiveConfirm();
   const notify = useNotify();
+  const { capabilities } = usePlatform();
+
+  // Use native Telegram back button in Mini App
+  useBackButton(() => navigate('/admin'));
 
   // Queries
   const { data: tariffsData, isLoading } = useQuery({
@@ -117,7 +135,15 @@ export default function AdminTariffs() {
       {/* 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.tariffs.title')}</h1>
             <p className="text-sm text-dark-400">{t('admin.tariffs.subtitle')}</p>