ix: use DashboardLayout wrapper in Buchhaltung page

frontend/src/pages/Buchhaltung.tsx

@@ -1,4 +1,5 @@
 import { useState, useEffect } from 'react';
+import DashboardLayout from '../components/dashboard/DashboardLayout';
 import {
   Box,
   Button,
@@ -806,6 +807,7 @@ export default function Buchhaltung() {
   };
 
   return (
+    <DashboardLayout>
       <Box sx={{ p: 3 }}>
         <Box sx={{ display: 'flex', alignItems: 'center', mb: 3, gap: 2 }}>
           <Typography variant="h4" fontWeight={700}>Buchhaltung</Typography>
@@ -839,5 +841,6 @@ export default function Buchhaltung() {
           />
         )}
       </Box>
+    </DashboardLayout>
   );
 }