Fix unencrypted Zeroconf payload detection

[Korshikov]

Fixes #1885

Summary

• Normalize string values of the Zeroconf encrypt TXT property.
• Preserve support for native boolean values.
• Parse "false" payloads through the existing plaintext JSON path.
• Add a regression test covering both False and "false".

Background

Some devices, including the SONOFF SAWF-08P, advertise the Zeroconf property as:

encrypt=false

After TXT properties are decoded, this becomes the Python string "false". The previous truthiness check treated that non-empty string as encrypted and attempted to access a nonexistent iv, causing repeated KeyError: 'iv' messages.

The payload itself is valid plaintext telemetry containing temperature, humidity, and CO₂ values.

Testing

98 passed

Tested with Python 3.14 and Home Assistant 2026.9.2.