refactor: log silent AttributeError catches, add _sync_class to remaining services, drop dead ctx slot

src/render_queue.py

@@ -28,6 +28,11 @@ class JobNotFoundError(Exception):
 class RenderQueue:
     _default_instance: Optional['RenderQueue'] = None
 
+    @classmethod
+    def _sync_class(cls) -> None:
+        if cls._default_instance is not None:
+            pass  # no class-level attributes to sync
+
     def __init__(self) -> None:
         self.engine: Optional[create_engine] = None
         self.session: Optional[Session] = None