Handle malformed Sonoff advertisements

[IoannisArmamentos]

Summary

Prevent malformed or unsupported Sonoff BLE advertisements from causing parser exceptions.

Problem

The Sonoff parser had two failure cases:

• Its initial length guard allowed payloads that were still too short for later encrypted-data processing, which could result in IndexError.
• An unknown Sonoff device type could leave device_type undefined when report_unknown was disabled, resulting in UnboundLocalError.

Fix

Require the minimum payload length actually needed by the parser before processing the advertisement.

Also ensure unknown Sonoff device types always return cleanly after the optional diagnostic logging path.

Known Sonoff S-MATE and R5 parsing remains unchanged.

Regression tests cover truncated advertisements and unknown device types.