Prepare Kalendartool for MPM and disable invites

components/admin/CreateCalendarForm.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 /** Formular zum Erstellen eines Kalenders (nur Admin). */
+import { appFetch } from '@/lib/client-fetch';
 import { useState } from 'react';
 import { useRouter } from 'next/navigation';
 import { Button, Card, ErrorMessage, Input, Label } from '@/components/ui/ui';
@@ -17,7 +18,7 @@ export function CreateCalendarForm() {
 
     const formData = new FormData(event.currentTarget);
     try {
-      const response = await fetch('/api/calendars', {
+      const response = await appFetch('/api/calendars', {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
         body: JSON.stringify({