fix(web): two api_v3 paths called names that no longer exist (#625)

The Pixlet editor stop route restarts the display after a SIGKILL with
_run_systemctl_command, which starlark.py never imported (since #554). The
Starlark device-location resolver fell back to _ensure_cache_manager, which
#609 deleted; the resolver already accepts no cache manager. Both raised
NameError on the rare path that reaches them. pyflakes finds no other
undefined names in src/ or web_interface/.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

web_interface/blueprints/api_v3/__init__.py

@@ -1712,7 +1712,7 @@ def _get_starlark_device_location() -> DeviceLocationResolver:
     global _starlark_device_location
     if _starlark_device_location is None:
         _starlark_device_location = DeviceLocationResolver(
-            getattr(api_v3, 'cache_manager', None) or _ensure_cache_manager(), logger)
+            getattr(api_v3, 'cache_manager', None), logger)
     return _starlark_device_location