Add MarketService write methods and clean up stubs

Add create_marketplace() and soft_delete_marketplace() to MarketService
protocol, SQL implementation, and stubs — centralises market CRUD that
was previously duplicated in blog and events app-level service files.

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

services/market_impl.py

@@ -10,7 +10,9 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from shared.models.market import Product
 from shared.models.market_place import MarketPlace
+from shared.browser.app.utils import utcnow
 from shared.contracts.dtos import MarketPlaceDTO, ProductDTO
+from shared.services.relationships import attach_child, detach_child
 
 
 def _mp_to_dto(mp: MarketPlace) -> MarketPlaceDTO:
@@ -55,3 +57,55 @@ class SqlMarketService:
             await session.execute(select(Product).where(Product.id == product_id))
         ).scalar_one_or_none()
         return _product_to_dto(product) if product else None
+
+    async def create_marketplace(
+        self, session: AsyncSession, container_type: str, container_id: int,
+        name: str, slug: str,
+    ) -> MarketPlaceDTO:
+        # Look for existing (including soft-deleted)
+        existing = (await session.execute(
+            select(MarketPlace).where(
+                MarketPlace.container_type == container_type,
+                MarketPlace.container_id == container_id,
+                MarketPlace.slug == slug,
+            )
+        )).scalar_one_or_none()
+
+        if existing:
+            if existing.deleted_at is not None:
+                existing.deleted_at = None  # revive
+                existing.name = name
+                await session.flush()
+                await attach_child(session, container_type, container_id, "market", existing.id)
+                return _mp_to_dto(existing)
+            raise ValueError(f'Market with slug "{slug}" already exists for this container.')
+
+        market = MarketPlace(
+            container_type=container_type, container_id=container_id,
+            name=name, slug=slug,
+        )
+        session.add(market)
+        await session.flush()
+        await attach_child(session, container_type, container_id, "market", market.id)
+        return _mp_to_dto(market)
+
+    async def soft_delete_marketplace(
+        self, session: AsyncSession, container_type: str, container_id: int,
+        slug: str,
+    ) -> bool:
+        market = (await session.execute(
+            select(MarketPlace).where(
+                MarketPlace.container_type == container_type,
+                MarketPlace.container_id == container_id,
+                MarketPlace.slug == slug,
+                MarketPlace.deleted_at.is_(None),
+            )
+        )).scalar_one_or_none()
+
+        if not market:
+            return False
+
+        market.deleted_at = utcnow()
+        await session.flush()
+        await detach_child(session, container_type, container_id, "market", market.id)
+        return True

services/stubs.py

@@ -92,6 +92,18 @@ class StubMarketService:
     async def product_by_id(self, session: AsyncSession, product_id: int) -> ProductDTO | None:
         return None
 
+    async def create_marketplace(
+        self, session: AsyncSession, container_type: str, container_id: int,
+        name: str, slug: str,
+    ) -> MarketPlaceDTO:
+        raise RuntimeError("MarketService not available")
+
+    async def soft_delete_marketplace(
+        self, session: AsyncSession, container_type: str, container_id: int,
+        slug: str,
+    ) -> bool:
+        return False
+
 
 class StubCartService:
     async def cart_summary(