Add beautifulsoup4 to dev dependencies

Required for HTML parsing in web caching tests.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: jinglemansweep

pyproject.toml

@@ -52,6 +52,7 @@ dev = [
     "flake8>=6.1.0",
     "mypy>=1.5.0",
     "pre-commit>=3.4.0",
+    "beautifulsoup4>=4.12.0",
     "types-paho-mqtt>=1.6.0",
     "types-PyYAML>=6.0.0",
 ]