resolve issues with new features

frontend/src/pages/AdminDashboard.tsx

@@ -1,6 +1,6 @@
 import { useState, useEffect } from 'react';
 import { Box, Tabs, Tab, Typography } from '@mui/material';
-import { Navigate, useSearchParams } from 'react-router-dom';
+import { Navigate, useNavigate, useSearchParams } from 'react-router-dom';
 import DashboardLayout from '../components/dashboard/DashboardLayout';
 import ServiceManagerTab from '../components/admin/ServiceManagerTab';
 import SystemHealthTab from '../components/admin/SystemHealthTab';
@@ -24,6 +24,7 @@ function TabPanel({ children, value, index }: TabPanelProps) {
 const ADMIN_TAB_COUNT = 6;
 
 function AdminDashboard() {
+  const navigate = useNavigate();
   const [searchParams] = useSearchParams();
   const [tab, setTab] = useState(() => {
     const t = Number(searchParams.get('tab'));
@@ -47,7 +48,7 @@ function AdminDashboard() {
       <Typography variant="h4" sx={{ mb: 3 }}>Administration</Typography>
 
       <Box sx={{ borderBottom: 1, borderColor: 'divider' }}>
-        <Tabs value={tab} onChange={(_e, v) => setTab(v)}>
+        <Tabs value={tab} onChange={(_e, v) => { setTab(v); navigate(`/admin?tab=${v}`, { replace: true }); }}>
           <Tab label="Services" />
           <Tab label="System" />
           <Tab label="Benutzer" />