Add attach/detach glue calls to menu items, markets, and page config CRUD

Wire up ContainerRelation tracking via attach_child/detach_child in:
- menu_items: create, update (re-link on post change), delete
- markets: create (including revive), soft_delete
- page config: creation in update_features and update_sumup routes

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

bp/post/admin/routes.py

@@ -82,6 +82,8 @@ def register():
         pc = PageConfig(container_type="page", container_id=post_id, features={})
         g.s.add(pc)
         await g.s.flush()
+        from glue.services.relationships import attach_child
+        await attach_child(g.s, "page", post_id, "page_config", pc.id)
 
     # Parse request body
     body = await request.get_json()
@@ -144,6 +146,8 @@ def register():
         pc = PageConfig(container_type="page", container_id=post_id, features={})
         g.s.add(pc)
         await g.s.flush()
+        from glue.services.relationships import attach_child
+        await attach_child(g.s, "page", post_id, "page_config", pc.id)
 
     form = await request.form
     merchant_code = (form.get("merchant_code") or "").strip()