Proxy support

Hi there! It would be great if proxy support could be added. OpenAI/Claude/OpenRouter aren't accessible in every country, so it's pretty important to be able to route traffic through a proxy.

P.S. I'm not talking about just changing the endpoint. I'm specifically referring to proxying requests—like being able to use OpenRouter directly in OpenMind with an https-proxy user:password@123.123.123.123:3128 setup.