Round the measurment figures to one decimal place

https://heatpumpmonitor.org/?add=measured_mean_flow_temp_coldest_day,measured_room_temp_coldest_day,measured_outside_temp_coldest_day

<img width="1920" height="912" alt="Image" src="https://github.com/user-attachments/assets/3d487c1c-3f39-4edb-b53d-ee513bfd5808" />