Remove MenuItem.post relationship to fix mapper init error

The back_populates="menu_items" referenced a relationship removed from
Post in the glue layer commit. MenuItem model kept for table preservation.

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

models/menu_item.py

@@ -1,16 +1,16 @@
 from datetime import datetime
 from typing import Optional
-from sqlalchemy.orm import Mapped, mapped_column, relationship
+from sqlalchemy.orm import Mapped, mapped_column
 from sqlalchemy import Integer, String, DateTime, ForeignKey, func
 from shared.db.base import Base
 
 
 class MenuItem(Base):
+    """Deprecated — kept so the table isn't dropped. Use glue.models.MenuNode."""
     __tablename__ = "menu_items"
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
 
-    # Foreign key to posts table
     post_id: Mapped[int] = mapped_column(
         Integer,
         ForeignKey("posts.id", ondelete="CASCADE"),
@@ -18,10 +18,8 @@ class MenuItem(Base):
         index=True
     )
 
-    # Order for sorting menu items
     sort_order: Mapped[int] = mapped_column(Integer, nullable=False, default=0, index=True)
 
-    # Timestamps
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True),
         server_default=func.now(),
@@ -37,6 +35,3 @@ class MenuItem(Base):
         DateTime(timezone=True),
         nullable=True
     )
-
-    # Relationship to Post
-    post: Mapped["Post"] = relationship("Post", back_populates="menu_items")