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/AdminBroadcasts.tsx

@@ -3,10 +3,23 @@ import { useNavigate } from 'react-router-dom';
 import { useQuery } from '@tanstack/react-query';
 import { useTranslation } from 'react-i18next';
 import { adminBroadcastsApi } from '../api/adminBroadcasts';
-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 BroadcastIcon = () => (
   <svg className="h-6 w-6" fill="none" viewBox="0 0 24 24" stroke="currentColor" strokeWidth={1.5}>
     <path
@@ -116,6 +129,10 @@ function StatusBadge({ status }: { status: string }) {
 export default function AdminBroadcasts() {
   const { t } = useTranslation();
   const navigate = useNavigate();
+  const { capabilities } = usePlatform();
+
+  // Use native Telegram back button in Mini App
+  useBackButton(() => navigate('/admin'));
 
   const [page, setPage] = useState(0);
   const limit = 20;
@@ -136,7 +153,15 @@ export default function AdminBroadcasts() {
       {/* Header */}
       <div className="flex items-center 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-bold text-dark-100">{t('admin.broadcasts.title')}</h1>
             <p className="text-sm text-dark-400">{t('admin.broadcasts.subtitle')}</p>