Honor configured proxy routes for auth refreshes (#34655)

## Why

ChatGPT token refresh requests need to follow the same configured routing policy as other authentication traffic, including environments that use the system proxy.

## What changed

- Require an `AuthRouteConfig` throughout login, logout, token refresh, personal access token, and agent identity flows.
- Build auth HTTP clients directly from that configuration instead of falling back to a default HTTP client when routing configuration is absent.

## Testing

- Add an integration test that refreshes a token through a cached system-proxy route and verifies the proxy receives the expected request.

GitOrigin-RevId: 7d54ab3219939a49921c51faf08cd4c2eabca51c

codex-rs/app-server/src/request_processors/account_processor.rs

@@ -464,7 +464,7 @@ impl AccountRequestProcessor {
                 config.forced_chatgpt_workspace_id.clone(),
                 config.cli_auth_credentials_store_mode,
                 config.auth_keyring_backend_kind(),
-                Some(config.auth_route_config()),
+                config.auth_route_config(),
             )
         };
         #[cfg(debug_assertions)]