Fix blog home route — replace services.cart with fetch_data

Missed cross-app call in blog/bp/blog/routes.py:127 caused
CartService not registered error on blog.rose-ash.com homepage.

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

blog/bp/blog/routes.py

@@ -84,7 +84,8 @@ def register(url_prefix, title):
       from ..post.services.post_data import post_data as _post_data
       from shared.config import config as get_config
       from shared.infrastructure.cart_identity import current_cart_identity
-      from shared.services.registry import services as svc
+      from shared.infrastructure.data_client import fetch_data
+      from shared.contracts.dtos import CartSummaryDTO, dto_from_dict
       from shared.infrastructure.fragments import fetch_fragment, fetch_fragments
 
       p_data = await _post_data("home", g.s, include_drafts=False)
@@ -121,13 +122,16 @@ def register(url_prefix, title):
           "container_nav_html": container_nav_html,
       }
 
-      # Page cart badge
+      # Page cart badge via HTTP
       if p_data["post"].get("is_page"):
           ident = current_cart_identity()
-          page_summary = await svc.cart.cart_summary(
-              g.s, user_id=ident["user_id"], session_id=ident["session_id"],
-              page_slug=post_slug,
-          )
+          summary_params = {"page_slug": post_slug}
+          if ident["user_id"] is not None:
+              summary_params["user_id"] = ident["user_id"]
+          if ident["session_id"] is not None:
+              summary_params["session_id"] = ident["session_id"]
+          raw_summary = await fetch_data("cart", "cart-summary", params=summary_params, required=False)
+          page_summary = dto_from_dict(CartSummaryDTO, raw_summary) if raw_summary else CartSummaryDTO()
           ctx["page_cart_count"] = page_summary.count + page_summary.calendar_count + page_summary.ticket_count
           ctx["page_cart_total"] = float(page_summary.total + page_summary.calendar_total + page_summary.ticket_total)