Dashboard-side urllib readers (gateway health probe, ElevenLabs voices)
and self-hosted OIDC httpx readers (discovery, token exchange, revocation)
buffered remote response bodies with no size bound — a hostile or
compromised upstream could exhaust memory. Both halves now read with a
1 MiB hard cap: a shared _read_dashboard_json_response for urllib JSON
reads and a streaming _request_limited_response for IdP endpoints that
prechecks Content-Length and caps the chunked body regardless.
Adapted from #54809 and #55122 (credit @ooiuuii) to current main, where
the token exchange lives in plugins/dashboard_auth/_shared.py and the
health probe in hermes_cli/web_server_gateway.py.
Fixes#54808, Fixes#55121
ca38caeea0