- Replace determine_if_https() with ProxyState.is_https field so X-Forwarded-Proto
reflects the listener's protocol instead of guessing from the Host header
- Return ProxyError::BadGateway with host/upstream context for non-connect upstream
errors instead of bare StatusCode::BAD_GATEWAY
- Implement InFlightCounter with RAII guard for tracking in-flight connections
- Add drain_in_flight() to wait for connections to complete on shutdown, with
configurable timeout before forcing exit
- Mark review/core-components and review/integration-readiness as complete
glm-5.1
cf002cc40f