When the OAuth gate is active, start_server runs uvicorn with
proxy_headers=True so the dashboard can honour X-Forwarded-Proto from
Fly's TLS terminator (cookies, redirect URI reconstruction). A side
effect: ws.client.host is rewritten to the X-Forwarded-For value, which
on Fly is the real internet client IP — never loopback. The loopback
peer guard in _ws_client_is_allowed then rejected every WS upgrade in
gated mode (4403 close) even after a successful OAuth round trip and
ticket consumption, silently breaking /api/pty, /api/ws, /api/pub, and
/api/events.
Fix: in gated mode, bypass the peer-IP check. The OAuth gate +
single-use ticket is the auth. The Host/Origin guard in
_ws_host_origin_is_allowed still runs and is what protects against
DNS-rebinding here, not the peer IP.
Loopback mode behaviour is unchanged: the legacy ?token= path is the
only auth there and we don't want LAN hosts guessing tokens.
Regression coverage: TestWsRequestIsAllowedGated pins all four
behaviours — non-loopback peer allowed in gated mode, non-loopback peer
rejected in loopback mode, loopback peer allowed in loopback mode, and
the Host/Origin guard still firing on a rebinding attempt with gated
mode + matching peer.