rework issue system

backend/src/services/vehicle.service.ts

@@ -653,7 +653,7 @@ class VehicleService {
   async getStatusHistory(fahrzeugId: string) {
     try {
       const result = await pool.query(
-        `SELECT h.*, u.display_name AS geaendert_von_name
+        `SELECT h.*, COALESCE(u.name, u.preferred_username, u.email) AS geaendert_von_name
          FROM fahrzeug_status_historie h
          LEFT JOIN users u ON u.id = h.geaendert_von
          WHERE h.fahrzeug_id = $1