The proxy configuration now uses a SOCKS5 scheme instead of MTProto. The default port is updated to 1080 and optional username/password fields are supported. Docker compose comments are updated accordingly.
BREAKING CHANGE: existing MTProto proxy settings (scheme "mtproto", port 443) are no longer supported and must be migrated to SOCKS5.
Introduce optional MTProto proxy configuration sourced from environment variables, expose related settings in `config.py`, document the variables in `dockercompose.yml`, and pass the proxy configuration to the Telegram client initialization.