chore(backend): drop dead code left by the InfraService refactor

Remove symbols with no remaining consumer:

- `gateway_name` property on Docker/MacosInfraService — nothing uses it; the
  launch flow reads `gateway().name` off the Gateway service. (+ its docker test.)
- firecracker `infra_vm` EGRESS_PORT / SUPERVISE_PORT / GIT_HTTP_PORT — dead
  duplicates; launch.py uses supervisor.types / docker.egress / a local const.
- macOS `INFRA_DB_VOLUME` back-compat alias — unused since the DB-volume test
  moved to `ORCHESTRATOR_DB_VOLUME`.
- docker `infra.py`: the unused `ORCHESTRATOR_SOURCE_HASH_LABEL` import and the
  `__all__` re-exports of the orchestrator constants (consumers import them from
  `docker.orchestrator`, not `docker.infra`).
- macOS `infra.py`: the unused `GatewayError` import + re-export.

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

bot_bottle/backend/macos_container/infra.py

@@ -38,7 +38,6 @@ from .gateway import (
     GATEWAY_IMAGE,
     GATEWAY_NAME,
     GATEWAY_NETWORK,
-    GatewayError,
     MacosGateway,
     ensure_networks,
 )
@@ -53,8 +52,6 @@ from .orchestrator import (
 # `INFRA_NAME` is kept — now aliasing the gateway container — for callers that
 # still import it (probe / reprovision attribute against the gateway).
 INFRA_NAME = GATEWAY_NAME
-# Back-compat alias: the DB volume moved to the orchestrator module.
-INFRA_DB_VOLUME = ORCHESTRATOR_DB_VOLUME
 
 _REPO_ROOT = Path(__file__).resolve().parents[3]
 
@@ -89,10 +86,6 @@ class MacosInfraService(InfraService):
         self._gateway_name = gateway_name
         self._db_volume = db_volume
 
-    @property
-    def gateway_name(self) -> str:
-        return self._gateway_name
-
     def orchestrator(self) -> MacosOrchestrator:
         """The control-plane service on the host-only control network. Cheap to
         reconstruct — the launch flow reads its `url()` / `gateway_url()` /
@@ -162,9 +155,7 @@ class MacosInfraService(InfraService):
 __all__ = [
     "MacosInfraService",
     "OrchestratorStartError",
-    "GatewayError",
     "ORCHESTRATOR_NAME",
     "INFRA_NAME",
-    "INFRA_DB_VOLUME",
     "probe_orchestrator_url",
 ]