feat: CalDAV-Integration für Admin-Kalender

- Neue CalDAV-Route mit PROPFIND und GET-Endpoints
- ICS-Format-Generator für Buchungsdaten
- Token-basierte Authentifizierung für CalDAV-Zugriff
- Admin-Interface mit CalDAV-Link-Generator
- Schritt-für-Schritt-Anleitung für Kalender-Apps
- 24h-Token-Ablaufzeit für Sicherheit
- Unterstützung für Outlook, Google Calendar, Apple Calendar, Thunderbird

Fixes: Admin kann jetzt Terminkalender in externen Apps abonnieren

src/client/components/admin-calendar.tsx

@@ -9,6 +9,10 @@ export function AdminCalendar() {
   const [sendDeleteEmail, setSendDeleteEmail] = useState(false);
   const [deleteActionType, setDeleteActionType] = useState<'delete' | 'cancel'>('delete');
   
+  // CalDAV state
+  const [caldavData, setCaldavData] = useState<any>(null);
+  const [showCaldavInstructions, setShowCaldavInstructions] = useState(false);
+  
   // Manual booking modal state
   const [showCreateModal, setShowCreateModal] = useState(false);
   const [createFormData, setCreateFormData] = useState({
@@ -77,6 +81,11 @@ export function AdminCalendar() {
     queryClient.bookings.proposeReschedule.mutationOptions()
   );
 
+  // CalDAV token generation mutation
+  const { mutate: generateCalDAVToken, isPending: isGeneratingToken } = useMutation(
+    queryClient.bookings.generateCalDAVToken.mutationOptions()
+  );
+
   const getTreatmentName = (treatmentId: string) => {
     return treatments?.find(t => t.id === treatmentId)?.name || "Unbekannte Behandlung";
   };
@@ -275,6 +284,31 @@ export function AdminCalendar() {
     });
   };
 
+  const handleGenerateCalDAVToken = () => {
+    const sessionId = localStorage.getItem('sessionId');
+    if (!sessionId) return;
+
+    generateCalDAVToken({
+      sessionId
+    }, {
+      onSuccess: (data) => {
+        setCaldavData(data);
+        setShowCaldavInstructions(true);
+      },
+      onError: (error: any) => {
+        console.error('CalDAV Token Generation Error:', error);
+      }
+    });
+  };
+
+  const copyToClipboard = (text: string) => {
+    navigator.clipboard.writeText(text).then(() => {
+      // Optional: Show success message
+    }).catch(err => {
+      console.error('Failed to copy text: ', err);
+    });
+  };
+
   return (
     <div className="max-w-7xl mx-auto">
       <h2 className="text-2xl font-bold text-gray-900 mb-6">Kalender - Bevorstehende Buchungen</h2>
@@ -307,6 +341,62 @@ export function AdminCalendar() {
         </div>
       </div>
 
+      {/* CalDAV Integration */}
+      <div className="bg-white rounded-lg shadow p-6 mb-6">
+        <div className="flex items-center justify-between mb-4">
+          <div>
+            <h3 className="text-lg font-semibold text-gray-900">Kalender-Abonnement</h3>
+            <p className="text-sm text-gray-600">Abonniere deinen Terminkalender in deiner Kalender-App</p>
+          </div>
+          <button
+            onClick={handleGenerateCalDAVToken}
+            disabled={isGeneratingToken}
+            className="px-4 py-2 bg-blue-600 text-white rounded-lg hover:bg-blue-700 disabled:opacity-50 disabled:cursor-not-allowed transition-colors text-sm font-medium"
+          >
+            {isGeneratingToken ? 'Generiere...' : 'CalDAV-Link erstellen'}
+          </button>
+        </div>
+        
+        {caldavData && (
+          <div className="border-t pt-4">
+            <div className="bg-gray-50 rounded-lg p-4 mb-4">
+              <div className="flex items-center justify-between mb-2">
+                <label className="text-sm font-medium text-gray-700">CalDAV-URL:</label>
+                <button
+                  onClick={() => copyToClipboard(caldavData.caldavUrl)}
+                  className="text-blue-600 hover:text-blue-800 text-sm"
+                >
+                  Kopieren
+                </button>
+              </div>
+              <input
+                type="text"
+                value={caldavData.caldavUrl}
+                readOnly
+                className="w-full p-2 bg-white border border-gray-300 rounded text-sm font-mono"
+              />
+              <div className="text-xs text-gray-500 mt-2">
+                Gültig bis: {new Date(caldavData.expiresAt).toLocaleString('de-DE')}
+              </div>
+            </div>
+            
+            <div className="text-sm text-gray-600">
+              <p className="mb-2">
+                <strong>So abonnierst du den Kalender:</strong>
+              </p>
+              <ul className="list-disc list-inside space-y-1 text-sm">
+                {caldavData.instructions.steps.map((step: string, index: number) => (
+                  <li key={index}>{step}</li>
+                ))}
+              </ul>
+              <p className="mt-3 text-amber-700 bg-amber-50 p-2 rounded">
+                <strong>Hinweis:</strong> {caldavData.instructions.note}
+              </p>
+            </div>
+          </div>
+        )}
+      </div>
+
       {/* Calendar */}
       <div className="bg-white rounded-lg shadow-lg overflow-hidden">
         {/* Calendar Header */}