HTTPS_PROXY env support

[gimmw]

Issue

HTTPS_PROXY environment variable not honored
Explicitly specifying the proxy in a Connection may not always be practical (upstream projects, dockerized environments).

Problem

Currently, when self.proxy is None (default), it's still explicitly passed to ws_connect() as proxy=None. This prevents aiohttp from using the environment variables (HTTPS_PROXY) even though trust_env=True is set on the session.

Suggested Workaround

In Communicate, fallback to env HTTPS_PROXY if proxy is None