// Package backendclient is the gateway-side adapter to the consolidated
// `backend` service. It bundles every gateway → backend conversation:
//
//   - public REST (`/api/v1/public/auth/*`) used by the public auth
//     surface,
//   - internal REST (`/api/v1/internal/sessions/*`,
//     `/api/v1/internal/users/*/account-internal`) used by the
//     authenticated request pipeline,
//   - authenticated user REST (`/api/v1/user/*`) used by the gRPC
//     downstream router after envelope verification,
//   - gRPC `Push.SubscribePush` used to receive `client_event` and
//     `session_invalidation` frames from backend.
//
// One env-driven Config describes the backend endpoint and the gateway
// client identity. A single Client value is wired by `cmd/gateway` and
// shared by all consumers (rest API public auth handler, gRPC session
// cache, downstream user/lobby routes, and the push subscriber).
package backendclient