Show welcome banner once per install (Python, JS, Docker).
Uses marker file in ~/.cloakbrowser/ — resets on cache clear or update.
Replaces logger.info() calls that were invisible by default.
Bump to v0.3.8.
Add cloakhq/cloakbrowser Docker Hub image with Node.js, JS wrapper,
Xvfb headed mode, and cloaktest shortcut. Add launch feedback and IP
display to all examples. Update README Docker section for Docker Hub.