Revert extend_existing workaround on MenuNode and ContainerRelation

The root cause (glue submodule) was fixed by removing it from app repos.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

models/menu_node.py

@@ -11,7 +11,6 @@ class MenuNode(Base):
     __table_args__ = (
         Index("ix_menu_nodes_container", "container_type", "container_id"),
         Index("ix_menu_nodes_parent_id", "parent_id"),
-        {"extend_existing": True},
     )
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)