(system_user)-fix change password. convert user_id UUID to str

app/system_users/services/service.py

@@ -631,7 +631,7 @@ class SystemUserService:
             
             # Update password
             await self.collection.update_one(
-                {"user_id": user_id},
+                {"user_id": str(user_id)},
                 {"$set": {
                     "password_hash": new_password_hash,
                     "security_settings.last_password_change": datetime.utcnow(),