Forward proxy (Boundary & Guacamole)

Route the admin backend's outbound calls to Boundary controllers and Guacamole servers through an HTTP/HTTPS forward proxy, for gateways behind a corporate proxy.

• Use proxy toggle, Proxy URL (http(s)://host:port), optional proxy username/password, and Verify TLS (controls the target gateway's certificate, independent of the proxy).
• Proxied requests carry an Agent/4999 User-Agent marker — add a matching allow rule on the proxy.