Function list_env_vars 

async fn list_env_vars() -> impl IntoResponse

GET /api/env-vars — the names of all environment variables available to the current process. Returns them sorted, with no values exposed.

Uses vars_os + to_string_lossy rather than std::env::vars(), which panics on a non-Unicode name or value — an environment the gateway process didn’t choose (inherited from its container/host) must not be able to take down this handler.