do_OPTIONS answered every CORS preflight with Access-Control-Allow-Origin: *,
advertising broader cross-origin access than a real request is granted — on a
password-less deployment that lets any site read authenticated responses. It now
echoes the request Origin only when _check_same_origin_browser_request approves
it (the exact same-origin / HERMES_WEBUI_ALLOWED_ORIGINS policy the CSRF gate
enforces for real requests), adds Vary: Origin, and never emits *. A disallowed
origin gets a 200 with no CORS headers (browser treats as preflight denial).
Default deployments (no allowlist) are unaffected.
Contributor stage; gate-pass. Co-authored-by: mo7al876any <mo7al876any@users.noreply.github.com>