Domain isolation: replace cross-domain imports with service calls

Replace direct Post, MarketPlace, Calendar model queries and HTTP API
calls with typed service calls. Events registers all 4 services via
domain_services_fn with has() guards.

Key changes:
- app.py: use domain_services_fn, Post/Calendar/MarketPlace queries
  → services.blog/calendar/market, HTTP cart API → services.cart
- calendars/markets services: Post → services.blog
- post_associations: Post → services.blog, direct queries → services
- markets routes: remove unused MarketPlace import
- glue imports → shared imports throughout

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

bp/markets/routes.py

@@ -3,9 +3,6 @@ from __future__ import annotations
 from quart import (
     request, render_template, make_response, Blueprint, g
 )
-from sqlalchemy import select
-
-from shared.models.market_place import MarketPlace
 
 from .services.markets import (
     create_market as svc_create_market,

bp/markets/services/markets.py

@@ -7,9 +7,9 @@ from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from shared.models.market_place import MarketPlace
-from shared.models.ghost_content import Post
 from shared.browser.app.utils import utcnow
-from glue.services.relationships import attach_child, detach_child
+from shared.services.registry import services
+from shared.services.relationships import attach_child, detach_child
 
 
 class MarketError(ValueError):
@@ -40,7 +40,7 @@ async def create_market(sess: AsyncSession, post_id: int, name: str) -> MarketPl
         raise MarketError("Market name must not be empty.")
     slug = slugify(name)
 
-    post = (await sess.execute(select(Post).where(Post.id == post_id))).scalar_one_or_none()
+    post = await services.blog.get_post_by_id(sess, post_id)
     if not post:
         raise MarketError(f"Post {post_id} does not exist.")
     if not post.is_page:
@@ -68,13 +68,15 @@ async def create_market(sess: AsyncSession, post_id: int, name: str) -> MarketPl
 
 
 async def soft_delete(sess: AsyncSession, post_slug: str, market_slug: str) -> bool:
+    post = await services.blog.get_post_by_slug(sess, post_slug)
+    if not post:
+        return False
+
     market = (
         await sess.execute(
-            select(MarketPlace)
-            .join(Post, MarketPlace.container_id == Post.id)
-            .where(MarketPlace.container_type == "page")
-            .where(
-                Post.slug == post_slug,
+            select(MarketPlace).where(
+                MarketPlace.container_type == "page",
+                MarketPlace.container_id == post.id,
                 MarketPlace.slug == market_slug,
                 MarketPlace.deleted_at.is_(None),
             )