Domain isolation: replace cross-domain imports with service calls

Replace direct Calendar, MarketPlace, and Post model queries with typed
service calls (services.blog, services.calendar, services.market,
services.cart). Blog registers all 4 services via domain_services_fn
with has() guards for composable deployment.

Key changes:
- app.py: use domain_services_fn instead of inline service registration
- admin routes: MarketPlace queries → services.market.marketplaces_for_container()
- entry_associations: CalendarEntryPost → services.calendar.entry_ids_for_content()
- markets service: Post query → services.blog.get_post_by_id/slug()
- posts_data, post routes: use calendar/market/cart services
- menu_items: glue imports → shared imports

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

bp/menu_items/services/menu_items.py

@@ -2,9 +2,9 @@ from __future__ import annotations
 
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select, func
-from glue.models.menu_node import MenuNode
+from shared.models.menu_node import MenuNode
 from models.ghost_content import Post
-from glue.services.relationships import attach_child, detach_child
+from shared.services.relationships import attach_child, detach_child
 
 
 class MenuItemError(ValueError):