Split cart into 4 microservices: relations, likes, orders, page-config→blog

Phase 1 - Relations service (internal): owns ContainerRelation, exposes
get-children data + attach/detach-child actions. Retargeted events, blog,
market callers from cart to relations.

Phase 2 - Likes service (internal): unified Like model replaces ProductLike
and PostLike with generic target_type/target_slug/target_id. Exposes
is-liked, liked-slugs, liked-ids data + toggle action.

Phase 3 - PageConfig → blog: moved ownership to blog with direct DB queries,
removed proxy endpoints from cart.

Phase 4 - Orders service (public): owns Order/OrderItem + SumUp checkout
flow. Cart checkout now delegates to orders via create-order action.
Webhook/return routes and reconciliation moved to orders.

Phase 5 - Infrastructure: docker-compose, deploy.sh, Dockerfiles updated
for all 3 new services. Added orders_url helper and factory model imports.

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

blog/bp/post/services/markets.py

@@ -41,7 +41,7 @@ async def create_market(sess: AsyncSession, post_id: int, name: str) -> MarketPl
     if not post.is_page:
         raise MarketError("Markets can only be created on pages, not posts.")
 
-    raw_pc = await fetch_data("cart", "page-config",
+    raw_pc = await fetch_data("blog", "page-config",
         params={"container_type": "page", "container_id": post_id},
         required=False)
     if raw_pc is None or not (raw_pc.get("features") or {}).get("market"):