The CORS middleware with the `access_control_allow_origin` origin wrapped every route from the router root, so the login and URL generator pages and `/metrics` sent `Access-Control-Allow-Origin` too. It now wraps only `/v1/image/` and `/v1/e/`, which form a `/v1` subrouter so that a browser's preflight `OPTIONS` request still gets its answer; the maintenance mode group moved inside it unchanged. Every other route sends no CORS headers. A new test checks both image routes, a preflight included, and the login and URL generator pages. `README.md` and `config.example.yml` say the setting covers the image routes only.
Unverified by test: `/metrics`, whose middleware registers with the process-wide Prometheus registry.
Model: opus-5-5
