Radiators show temperature 0 instead of unavailable when cloud contact is lost

[Koffeinuser]

Problem

When an Adax radiator loses connection to the Adax cloud, the API returns "temperature": 0 in the room object. The library stores this as 0.0 without any indication that the value is invalid:

room["temperature"] = room.get("temperature", 0) / 100.0

Since 0 is never a valid indoor temperature, this is clearly a sentinel value meaning "no data from device" — but callers of the library have no way to distinguish it from a real reading.

Suggested fix

raw_temp = room.get("temperature", 0)
room["temperature"] = raw_temp / 100.0 if raw_temp != 0 else None

Returning None when the raw value is 0 correctly signals to callers that no temperature data is available.

Context

Discovered while using Adax radiators in my Home Assistant integration. When a radiator goes offline, the integration keeps showing 0.0°C as a valid reading with no way to detect the failure. The native Adax app also shows no temperature in this state, confirming it is an offline/disconnected condition. Returning None would allow integrations to properly handle this case (e.g. mark the device as unavailable).