Add TLS encryption and username/password authentication support for
the KumoProxy SOCKS5 server, with full Lua configuration capabilities.
Proxy Server Changes:
- Add kumo.start_proxy_listener() Lua function with TLS support
- Add proxy_server_auth_rfc1929 event for Lua-based auth validation
- Return AuthInfo from auth for ACL system integration
- Support optional and required authentication modes
- Maintain backwards-compatible legacy CLI mode (--listen, --timeout-seconds)
Breaking Changes:
- Cache renamed from rfc5321_rustls_config to rustls_client_config
Refs: #451
Closes: 459
