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/calendars/services/calendars.py

@@ -4,8 +4,8 @@ from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from models.calendars import Calendar
-from shared.models.ghost_content import Post  # for FK existence checks
-from glue.services.relationships import attach_child, detach_child
+from shared.services.registry import services
+from shared.services.relationships import attach_child, detach_child
 import unicodedata
 import re
 
@@ -49,13 +49,15 @@ def slugify(value: str, max_len: int = 255) -> str:
 
 
 async def soft_delete(sess: AsyncSession, post_slug: str, calendar_slug: str) -> bool:
+    post = await services.blog.get_post_by_slug(sess, post_slug)
+    if not post:
+        return False
+
     cal = (
         await sess.execute(
-            select(Calendar)
-            .join(Post, Calendar.container_id == Post.id)
-            .where(Calendar.container_type == "page")
-            .where(
-                Post.slug == post_slug,
+            select(Calendar).where(
+                Calendar.container_type == "page",
+                Calendar.container_id == post.id,
                 Calendar.slug == calendar_slug,
                 Calendar.deleted_at.is_(None),
             )
@@ -82,7 +84,7 @@ async def create_calendar(sess: AsyncSession, post_id: int, name: str) -> Calend
     slug=slugify(name)
 
     # Ensure post exists (avoid silent FK errors in some DBs)
-    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 CalendarError(f"Post {post_id} does not exist.")