Addition of a missing Funktion

Web/app.py

@@ -10373,6 +10373,14 @@ def my_borrowed_items():
     )
 
 
+@app.route('/api/push/vapid-key', methods=['GET'])
+def get_vapid_key():
+    """Returns the VAPID public key for web push subscriptions."""
+    from Web.push_notifications import _get_vapid_public
+    if not _get_vapid_public():
+        return jsonify({'error': 'VAPID public key not configured'}), 500
+    return jsonify({'publicKey': _get_vapid_public()})
+
 @app.route('/notifications')
 def notifications_view():
     """Notification center for users and admins."""