refactor(App, MikrotikBackupsManager): remove unused IconDatabaseBackup and update icon reference for Mikrotik backups

frontend/src/App.jsx

@@ -20,8 +20,7 @@ import {
   IconDownload,
   IconCreditCard,
   IconMenu2,
-  IconArrowsExchange,
-  IconDatabaseBackup
+  IconArrowsExchange
 } from '@tabler/icons-react';
 import ServerManager from './ServerManager';
 import FilterManager from './FilterManager';
@@ -204,7 +203,7 @@ function MainLayout() {
       icon: IconSettings,
       items: [
         { id: 'auto-urls', title: t('autoUrls'), path: '/auto-urls', icon: IconDownload },
-        { id: 'mikrotik-backups', title: t('mikrotikBackups'), path: '/mikrotik-backups', icon: IconDatabaseBackup }
+        { id: 'mikrotik-backups', title: t('mikrotikBackups'), path: '/mikrotik-backups', icon: IconDatabase }
       ]
     },
     // Убрали неиспользуемые/неработающие разделы

frontend/src/MikrotikBackupsManager.jsx

@@ -7,7 +7,6 @@ import EmptyState from './components/EmptyState.jsx';
 import Tooltip from './components/Tooltip.jsx';
 import ServerAutocompleteInput from './components/ServerAutocompleteInput.jsx';
 import {
-  IconDatabaseBackup,
   IconRefresh,
   IconAlertTriangle,
   IconEye,