Decouple blog UI via widget registry

Replace explicit calendar/market service calls in post routes, auth
routes, and listing cards with widget-driven iteration. Zero cross-domain
imports remain in blog bp layer.

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

bp/blog/services/posts_data.py

@@ -1,7 +1,7 @@
 from ..ghost_db import DBClient  # adjust import path
 from sqlalchemy import select
 from models.ghost_content import PostLike
-from shared.services.registry import services
+from shared.services.widget_registry import widgets
 from quart import g
 
 async def posts_data(
@@ -85,12 +85,11 @@ async def posts_data(
       for post in posts:
           post["is_liked"] = False
 
-  # Fetch associated entries for each post via calendar service
-  entries_by_post = await services.calendar.confirmed_entries_for_posts(session, post_ids)
-
-  # Add associated_entries to each post
-  for post in posts:
-      post["associated_entries"] = entries_by_post.get(post["id"], [])
+  # Widget-driven card decoration
+  for w in widgets.container_cards:
+      batch_data = await w.batch_fn(session, post_ids)
+      for post in posts:
+          post[w.context_key] = batch_data.get(post["id"], [])
 
   tags=await client.list_tags(
     limit=50000