Migration CPP

• Migrate project to native C++ runtime and consolidate docs

• Add HTTPAceProxyCPP as the maintained C++20 implementation
• Move the deprecated Python implementation under httpaceproxypy
• Copy the web UI into httpaceproxycpp so the C++ image is self-contained
• Add root docker-compose-aio.yml for AceServe + HTTPAceProxyCPP
• Update Docker workflows to build the C++ Docker image
• Simplify README around the new C++ version and Python deprecation
• Consolidate documentation under doc/
• Keep dedicated docs for plugin management and Nginx/NPM setup
• Remove duplicated and outdated legacy documentation