Decouple PageConfig cross-domain queries + merge cart into db_market

PageConfig (db_blog) decoupling:
- Blog: add page-config, page-config-by-id, page-configs-batch data endpoints
- Blog: add update-page-config action endpoint for events payment admin
- Cart: hydrate_page, resolve_page_config, get_cart_grouped_by_page all
  fetch PageConfig from blog via HTTP instead of direct DB query
- Cart: check_sumup_status auto-fetches page_config from blog when needed
- Events: payment routes read/write PageConfig via blog HTTP endpoints
- Order model: remove cross-domain page_config ORM relationship (keep column)

Cart + Market DB merge:
- Cart tables (cart_items, orders, order_items) moved into db_market
- Cart app DATABASE_URL now points to db_market (same bounded context)
- CartItem.product / CartItem.market_place relationships work again
  (same database, no cross-domain join issues)
- Updated split-databases.sh, init-databases.sql, docker-compose.yml

Ghost sync fix:
- Wrap PostAuthor/PostTag delete+re-add in no_autoflush block
- Use synchronize_session="fetch" to keep identity map consistent
- Prevents query-invoked autoflush IntegrityError on composite PK

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

events/bp/payments/routes.py

@@ -1,12 +1,13 @@
 from __future__ import annotations
 
+from types import SimpleNamespace
+
 from quart import (
     render_template, make_response, Blueprint, g, request
 )
-from sqlalchemy import select
-
-from shared.models.page_config import PageConfig
 
+from shared.infrastructure.data_client import fetch_data
+from shared.infrastructure.actions import call_action
 from shared.browser.app.authz import require_admin
 from shared.browser.app.utils.htmx import is_htmx_request
 
@@ -19,20 +20,23 @@ def register():
         return {}
 
     async def _load_payment_ctx():
-        """Load PageConfig SumUp data for the current page."""
+        """Load PageConfig SumUp data for the current page (from blog)."""
         post = (getattr(g, "post_data", None) or {}).get("post", {})
         post_id = post.get("id")
         if not post_id:
             return {}
 
-        pc = (await g.s.execute(
-            select(PageConfig).where(PageConfig.container_type == "page", PageConfig.container_id == post_id)
-        )).scalar_one_or_none()
+        raw_pc = await fetch_data(
+            "blog", "page-config",
+            params={"container_type": "page", "container_id": post_id},
+            required=False,
+        )
+        pc = SimpleNamespace(**raw_pc) if raw_pc else None
 
         return {
-            "sumup_configured": bool(pc and pc.sumup_api_key),
-            "sumup_merchant_code": (pc.sumup_merchant_code or "") if pc else "",
-            "sumup_checkout_prefix": (pc.sumup_checkout_prefix or "") if pc else "",
+            "sumup_configured": bool(pc and getattr(pc, "sumup_api_key", None)),
+            "sumup_merchant_code": (getattr(pc, "sumup_merchant_code", None) or "") if pc else "",
+            "sumup_checkout_prefix": (getattr(pc, "sumup_checkout_prefix", None) or "") if pc else "",
         }
 
     @bp.get("/")
@@ -48,31 +52,27 @@ def register():
     @bp.put("/")
     @require_admin
     async def update_sumup(**kwargs):
-        """Update SumUp credentials for this page."""
+        """Update SumUp credentials for this page (writes to blog's db_blog)."""
         post = (getattr(g, "post_data", None) or {}).get("post", {})
         post_id = post.get("id")
         if not post_id:
             return await make_response("Post not found", 404)
 
-        pc = (await g.s.execute(
-            select(PageConfig).where(PageConfig.container_type == "page", PageConfig.container_id == post_id)
-        )).scalar_one_or_none()
-        if pc is None:
-            pc = PageConfig(container_type="page", container_id=post_id, features={})
-            g.s.add(pc)
-            await g.s.flush()
-
         form = await request.form
         merchant_code = (form.get("merchant_code") or "").strip()
         api_key = (form.get("api_key") or "").strip()
         checkout_prefix = (form.get("checkout_prefix") or "").strip()
 
-        pc.sumup_merchant_code = merchant_code or None
-        pc.sumup_checkout_prefix = checkout_prefix or None
+        payload = {
+            "container_type": "page",
+            "container_id": post_id,
+            "sumup_merchant_code": merchant_code,
+            "sumup_checkout_prefix": checkout_prefix,
+        }
         if api_key:
-            pc.sumup_api_key = api_key
+            payload["sumup_api_key"] = api_key
 
-        await g.s.flush()
+        await call_action("blog", "update-page-config", payload=payload)
 
         ctx = await _load_payment_ctx()
         html = await render_template("_types/payments/_main_panel.html", **ctx)