calendar and vehicle booking rework

frontend/src/components/shared/Sidebar.tsx

@@ -27,6 +27,7 @@ import {
   ExpandLess,
   LocalShipping,
   BugReport,
+  BookOnline,
 } from '@mui/icons-material';
 import { useNavigate, useLocation } from 'react-router-dom';
 import { useQuery } from '@tanstack/react-query';
@@ -49,11 +50,6 @@ interface NavigationItem {
   permission?: string;
 }
 
-const kalenderSubItems: SubItem[] = [
-  { text: 'Veranstaltungen', path: '/kalender' },
-  { text: 'Fahrzeugbuchungen', path: '/fahrzeugbuchungen' },
-];
-
 const adminSubItems: SubItem[] = [
   { text: 'Services', path: '/admin?tab=0' },
   { text: 'System', path: '/admin?tab=1' },
@@ -77,9 +73,14 @@ const baseNavigationItems: NavigationItem[] = [
     text: 'Kalender',
     icon: <CalendarMonth />,
     path: '/kalender',
-    subItems: kalenderSubItems,
     permission: 'kalender:view',
   },
+  {
+    text: 'Fahrzeugbuchungen',
+    icon: <BookOnline />,
+    path: '/fahrzeugbuchungen',
+    permission: 'fahrzeugbuchungen:view',
+  },
   {
     text: 'Fahrzeuge',
     icon: <DirectionsCar />,