Add raw protocol debug logging

[hilman2]

Summary

• add a dedicated raw protocol debug logger for HTTP and WebSocket traffic
• capture raw text frames and binary WS payloads before parsing/stripping
• document how to enable the logger and cover the new behavior with tests

Testing

• wsl -d Ubuntu -- bash -lc 'source ~/venvs/ha-xtool-s1/bin/activate && cd /mnt/d/Git/ha-xtool-s1 && black --check custom_components/xtool_s1/api.py tests/test_api.py'
• wsl -d Ubuntu -- bash -lc 'source ~/venvs/ha-xtool-s1/bin/activate && cd /mnt/d/Git/ha-xtool-s1 && ruff check custom_components/xtool_s1/api.py tests/test_api.py'
• wsl -d Ubuntu -- bash -lc 'source ~/venvs/ha-xtool-s1/bin/activate && cd /mnt/d/Git/ha-xtool-s1 && pytest -q'