refactor(docker): rename OrchestratorService -> DockerInfraService, move to backend/docker

OrchestratorService wasn't the orchestrator — it's the host-side lifecycle of
the docker infra *container* (the one that runs the Orchestrator). It read as
"the orchestrator as a service" and lived in orchestrator/lifecycle.py, while
its siblings (macOS MacosInfraService, Firecracker infra_vm) live under their
backend package. Rename it DockerInfraService and move it to
backend/docker/infra.py alongside the docker backend, with its docker-only
constants (INFRA_*/ORCHESTRATOR_* image + container names, daemon list, mount
paths).

orchestrator/lifecycle.py keeps only the backend-neutral pieces the other infra
services share — DEFAULT_PORT, DEFAULT_STARTUP_TIMEOUT_SECONDS,
OrchestratorStartError, source_hash — which macOS / firecracker / client still
import from there. backend/docker/infra.py imports those (backend -> orchestrator
is an allowed direction). Renamed the unit test to test_docker_infra.py.

Full unit suite green (2243).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot_bottle/backend/docker/launch.py

@@ -66,7 +66,7 @@ from .compose import (
 from .consolidated_compose import consolidated_agent_compose
 from ...orchestrator.store.config_store import resolve_teardown_timeout
 from .consolidated_launch import launch_consolidated, teardown_consolidated
-from ...orchestrator.lifecycle import INFRA_NAME
+from .infra import INFRA_NAME
 from .gateway import DockerGateway