Decouple per-service Alembic migrations and fix cross-DB queries

Each service (blog, market, cart, events, federation, account) now owns
its own database schema with independent Alembic migrations. Removes the
monolithic shared/alembic/ that ran all migrations against a single DB.

- Add per-service alembic.ini, env.py, and 0001_initial.py migrations
- Add shared/db/alembic_env.py helper with table-name filtering
- Fix cross-DB FK in blog/models/snippet.py (users lives in db_account)
- Fix cart_impl.py cross-DB queries: fetch products and market_places
  via internal data endpoints instead of direct SQL joins
- Fix blog ghost_sync to fetch page_configs from cart via data endpoint
- Add products-by-ids and page-config-ensure data endpoints
- Update all entrypoint.sh to create own DB and run own migrations
- Cart now uses db_cart instead of db_market
- Add docker-compose.dev.yml, dev.sh for local development
- CI deploys both rose-ash swarm stack and rose-ash-dev compose stack
- Fix Quart namespace package crash (root_path in factory.py)

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

cart/bp/data/routes.py

@@ -42,4 +42,39 @@ def register() -> Blueprint:
 
     _handlers["cart-summary"] = _cart_summary
 
+    # --- page-config-ensure ---
+    async def _page_config_ensure():
+        """Get or create a PageConfig for a container_type + container_id."""
+        from sqlalchemy import select
+        from shared.models.page_config import PageConfig
+
+        container_type = request.args.get("container_type", "page")
+        container_id = request.args.get("container_id", type=int)
+        if container_id is None:
+            return {"error": "container_id required"}, 400
+
+        row = (await g.s.execute(
+            select(PageConfig).where(
+                PageConfig.container_type == container_type,
+                PageConfig.container_id == container_id,
+            )
+        )).scalar_one_or_none()
+
+        if row is None:
+            row = PageConfig(
+                container_type=container_type,
+                container_id=container_id,
+                features={},
+            )
+            g.s.add(row)
+            await g.s.flush()
+
+        return {
+            "id": row.id,
+            "container_type": row.container_type,
+            "container_id": row.container_id,
+        }
+
+    _handlers["page-config-ensure"] = _page_config_ensure
+
     return bp