fix(hosting): require merchant or prospect for site creation

- Schema: add merchant_id/prospect_id with model_validator requiring
  at least one. Remove from-prospect endpoint (unified into POST /sites)
- Service: rewrite create() — if merchant_id use it directly, if
  prospect_id auto-create merchant from prospect data. Remove system
  merchant hack entirely. Extract _create_merchant_from_prospect helper.
- Simplify accept_proposal() — merchant already exists at creation,
  only creates subscription and marks prospect converted
- Tests: update all create calls with merchant_id, replace from-prospect
  tests with prospect_id + validation tests

Closes docs/proposals/hosting-site-creation-fix.md

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/hosting/services/hosted_site_service.py

@@ -88,12 +88,19 @@ class HostedSiteService:
         return sites, total
 
     def create(self, db: Session, data: dict) -> HostedSite:
-        """Create a hosted site with an auto-created Store on the hosting platform."""
-        from app.modules.tenancy.models import Platform
+        """Create a hosted site with an auto-created Store on the hosting platform.
+
+        Requires either merchant_id or prospect_id in data:
+        - merchant_id: store created under this merchant
+        - prospect_id: merchant auto-created from prospect data
+        """
+        from app.modules.tenancy.models import Merchant, Platform, Store
         from app.modules.tenancy.schemas.store import StoreCreate
         from app.modules.tenancy.services.admin_service import admin_service
 
         business_name = data["business_name"]
+        merchant_id = data.get("merchant_id")
+        prospect_id = data.get("prospect_id")
         slug = _slugify(business_name)
 
         # Find hosting platform
@@ -101,37 +108,25 @@ class HostedSiteService:
         if not platform:
             raise ValueError("Hosting platform not found. Run init_production first.")
 
-        # Create a temporary merchant-less store requires a merchant_id.
-        # For POC sites we create a placeholder: the store is re-assigned on accept_proposal.
-        # Use the platform's own admin store or create under a system merchant.
-        # For now, create store via AdminService which handles defaults.
-        store_code = slug.upper().replace("-", "_")[:50]
-        subdomain = slug
+        # Resolve merchant
+        if merchant_id:
+            merchant = db.query(Merchant).filter(Merchant.id == merchant_id).first()
+            if not merchant:
+                raise ValueError(f"Merchant {merchant_id} not found")
+        elif prospect_id:
+            merchant = self._create_merchant_from_prospect(db, prospect_id, data)
+        else:
+            raise ValueError("Either merchant_id or prospect_id is required")
 
         # Check for duplicate subdomain
-        from app.modules.tenancy.models import Store
-
+        subdomain = slug
         existing = db.query(Store).filter(Store.subdomain == subdomain).first()
         if existing:
             raise DuplicateSlugException(subdomain)
 
-        # We need a system merchant for POC sites.
-        # Look for one or create if needed.
-        from app.modules.tenancy.models import Merchant
-
-        system_merchant = db.query(Merchant).filter(Merchant.name == "HostWizard System").first()
-        if not system_merchant:
-            system_merchant = Merchant(
-                name="HostWizard System",
-                contact_email="system@hostwizard.lu",
-                is_active=True,
-                is_verified=True,
-            )
-            db.add(system_merchant)
-            db.flush()
-
+        store_code = slug.upper().replace("-", "_")[:50]
         store_data = StoreCreate(
-            merchant_id=system_merchant.id,
+            merchant_id=merchant.id,
             store_code=store_code,
             subdomain=subdomain,
             name=business_name,
@@ -142,7 +137,7 @@ class HostedSiteService:
 
         site = HostedSite(
             store_id=store.id,
-            prospect_id=data.get("prospect_id"),
+            prospect_id=prospect_id,
             status=HostedSiteStatus.DRAFT,
             business_name=business_name,
             contact_name=data.get("contact_name"),
@@ -153,12 +148,14 @@ class HostedSiteService:
         db.add(site)
         db.flush()
 
-        logger.info("Created hosted site: %s (store_id=%d)", site.display_name, store.id)
+        logger.info("Created hosted site: %s (store_id=%d, merchant_id=%d)", site.display_name, store.id, merchant.id)
         return site
 
-    def create_from_prospect(self, db: Session, prospect_id: int) -> HostedSite:
-        """Create a hosted site pre-filled from prospect data."""
+    def _create_merchant_from_prospect(self, db: Session, prospect_id: int, data: dict):
+        """Create a merchant from prospect data."""
         from app.modules.prospecting.models import Prospect
+        from app.modules.tenancy.schemas.merchant import MerchantCreate
+        from app.modules.tenancy.services.merchant_service import merchant_service
 
         prospect = db.query(Prospect).filter(Prospect.id == prospect_id).first()
         if not prospect:
@@ -166,20 +163,29 @@ class HostedSiteService:
 
             raise ProspectNotFoundException(str(prospect_id))
 
-        # Get primary contact info from prospect contacts
+        # Get contact info: prefer form data, fall back to prospect contacts
         contacts = prospect.contacts or []
-        primary_email = next((c.value for c in contacts if c.contact_type == "email"), None)
-        primary_phone = next((c.value for c in contacts if c.contact_type == "phone"), None)
-        contact_name = next((c.label for c in contacts if c.label), None)
+        email = (
+            data.get("contact_email")
+            or next((c.value for c in contacts if c.contact_type == "email"), None)
+            or f"contact-{prospect_id}@hostwizard.lu"
+        )
+        phone = data.get("contact_phone") or next(
+            (c.value for c in contacts if c.contact_type == "phone"), None
+        )
+        business_name = data.get("business_name") or prospect.business_name or prospect.domain_name
 
-        data = {
-            "business_name": prospect.business_name or prospect.domain_name or f"Prospect #{prospect.id}",
-            "contact_name": contact_name,
-            "contact_email": primary_email,
-            "contact_phone": primary_phone,
-            "prospect_id": prospect.id,
-        }
-        return self.create(db, data)
+        merchant_data = MerchantCreate(
+            name=business_name,
+            contact_email=email,
+            contact_phone=phone,
+            owner_email=email,
+        )
+        merchant, _owner_user, _temp_password = merchant_service.create_merchant_with_owner(
+            db, merchant_data
+        )
+        logger.info("Created merchant %s from prospect %d", merchant.name, prospect_id)
+        return merchant
 
     def update(self, db: Session, site_id: int, data: dict) -> HostedSite:
         site = self.get_by_id(db, site_id)
@@ -227,37 +233,25 @@ class HostedSiteService:
     def accept_proposal(
         self, db: Session, site_id: int, merchant_id: int | None = None
     ) -> HostedSite:
-        """Accept proposal: create or link merchant, create subscription, mark converted."""
+        """Accept proposal: create subscription, mark prospect converted.
+
+        The merchant already exists (assigned at site creation time).
+        Optionally pass merchant_id to reassign to a different merchant.
+        """
         site = self._transition(db, site_id, HostedSiteStatus.ACCEPTED)
         site.proposal_accepted_at = datetime.now(UTC)
 
         from app.modules.tenancy.models import Merchant, Platform
 
+        # Use provided merchant_id to reassign, or keep existing store merchant
         if merchant_id:
-            # Link to existing merchant
             merchant = db.query(Merchant).filter(Merchant.id == merchant_id).first()
             if not merchant:
                 raise ValueError(f"Merchant {merchant_id} not found")
+            site.store.merchant_id = merchant.id
+            db.flush()
         else:
-            # Create new merchant from contact info
-            from app.modules.tenancy.schemas.merchant import MerchantCreate
-            from app.modules.tenancy.services.merchant_service import merchant_service
-
-            email = site.contact_email or f"contact-{site.id}@hostwizard.lu"
-            merchant_data = MerchantCreate(
-                name=site.business_name,
-                contact_email=email,
-                contact_phone=site.contact_phone,
-                owner_email=email,
-            )
-            merchant, _owner_user, _temp_password = merchant_service.create_merchant_with_owner(
-                db, merchant_data
-            )
-            logger.info("Created merchant %s for site %d", merchant.name, site_id)
-
-        # Re-assign store to the real merchant
-        site.store.merchant_id = merchant.id
-        db.flush()
+            merchant = site.store.merchant
 
         # Create MerchantSubscription on hosting platform
         platform = db.query(Platform).filter(Platform.code == "hosting").first()
@@ -286,7 +280,6 @@ class HostedSiteService:
             prospect = db.query(Prospect).filter(Prospect.id == site.prospect_id).first()
             if prospect and prospect.status != ProspectStatus.CONVERTED:
                 prospect.status = ProspectStatus.CONVERTED
-                db.flush()
 
         db.flush()
         logger.info("Proposal accepted for site %d (merchant=%d)", site_id, merchant.id)