Bound Sonoff debug logging

[aferende]

Summary

The optional Sonoff debug view currently raises the integration logger to DEBUG and lets the protocol logger propagate to Home Assistant's raw log stream. Long-running debug mode can therefore write high-frequency Cloud/Local protocol traces to Home Assistant logs and, when configured, associated system-log/recorder processing.

This change keeps the existing bounded in-memory debug page while preventing protocol DEBUG records from propagating to Home Assistant's root handlers. WARNING and ERROR records are still explicitly forwarded, so actionable failures remain visible.

Changes

• Add a warning/error passthrough handler for the Sonoff logger.
• Disable propagation after attaching the optional debug view.
• Stop mutating LogRecord.levelno as a side effect of debug capture.
• Add regression coverage proving that a protocol debug trace stays in the view while an actionable warning reaches the root logger.

Impact

This makes temporary debugging safer for production Home Assistant installations: diagnostics remain available at the random debug-view URL, but protocol traffic no longer grows the raw log stream continuously.

Validation

• python3 -m compileall -q custom_components tests
• git diff --check

The regression test is included; the local environment used for this contribution does not have the project's pytest/Home Assistant test dependencies installed.

No configuration, credentials, device identifiers, or private-network information are included.