Native iOS/macOS apps do not send an Origin header in WebSocket connections.
The gateway checkBrowserOrigin() fails immediately on null origin before any
allowedOrigins check can run. Injecting Origin at the HAProxy ingress level
gives the gateway a valid origin to validate against the existing allowedOrigins
list (https://openclaw.apps.lab.apilab.us).
Related: openclaw/openclaw#24055, #35030, #35109