Decouple blog: use shared.models for all cross-app imports

- Replace all imports from cart.models, market.models, events.models
  with shared.models equivalents
- Convert blog/models/ghost_content.py to re-export stub
- Update shared + glue submodule pointers

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

bp/post/admin/routes.py

@@ -22,7 +22,7 @@ def register():
   @require_admin
   async def admin(slug: str):
     from shared.browser.app.utils.htmx import is_htmx_request
-    from cart.models.page_config import PageConfig
+    from shared.models.page_config import PageConfig
     from sqlalchemy import select as sa_select
 
     # Load features for page admin
@@ -62,7 +62,7 @@ def register():
   @require_admin
   async def update_features(slug: str):
     """Update PageConfig.features for a page."""
-    from cart.models.page_config import PageConfig
+    from shared.models.page_config import PageConfig
     from models.ghost_content import Post
     from sqlalchemy import select as sa_select
     from quart import jsonify
@@ -129,7 +129,7 @@ def register():
   @require_admin
   async def update_sumup(slug: str):
     """Update PageConfig SumUp credentials for a page."""
-    from cart.models.page_config import PageConfig
+    from shared.models.page_config import PageConfig
     from sqlalchemy import select as sa_select
     from quart import jsonify
 
@@ -191,7 +191,7 @@ def register():
   @require_admin
   async def calendar_view(slug: str, calendar_id: int):
     """Show calendar month view for browsing entries"""
-    from events.models.calendars import Calendar
+    from shared.models.calendars import Calendar
     from sqlalchemy import select
     from datetime import datetime, timezone
     from quart import request
@@ -273,7 +273,7 @@ def register():
   @require_admin
   async def entries(slug: str):
     from ..services.entry_associations import get_post_entry_ids
-    from events.models.calendars import Calendar
+    from shared.models.calendars import Calendar
     from sqlalchemy import select
 
     post_id = g.post_data["post"]["id"]
@@ -309,7 +309,7 @@ def register():
   @require_admin
   async def toggle_entry(slug: str, entry_id: int):
     from ..services.entry_associations import toggle_entry_association, get_post_entry_ids, get_associated_entries
-    from events.models.calendars import Calendar
+    from shared.models.calendars import Calendar
     from sqlalchemy import select
     from quart import jsonify
 
@@ -603,7 +603,7 @@ def register():
   @require_admin
   async def markets(slug: str):
     """List markets for this page."""
-    from market.models.market_place import MarketPlace
+    from shared.models.market_place import MarketPlace
     from sqlalchemy import select as sa_select
 
     post = (g.post_data or {}).get("post", {})
@@ -631,7 +631,7 @@ def register():
   async def create_market(slug: str):
     """Create a new market for this page."""
     from ..services.markets import create_market as _create_market, MarketError
-    from market.models.market_place import MarketPlace
+    from shared.models.market_place import MarketPlace
     from sqlalchemy import select as sa_select
     from quart import jsonify
 
@@ -669,7 +669,7 @@ def register():
   async def delete_market(slug: str, market_slug: str):
     """Soft-delete a market."""
     from ..services.markets import soft_delete_market
-    from market.models.market_place import MarketPlace
+    from shared.models.market_place import MarketPlace
     from sqlalchemy import select as sa_select
     from quart import jsonify