fix(tenancy): use correct Merchant.name field in team service

merchant_store_service referenced merchant.business_name and
merchant.brand_name which don't exist on the Merchant model.
The field is simply merchant.name.

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

app/modules/tenancy/services/merchant_store_service.py

@@ -424,7 +424,7 @@ class MerchantStoreService:
             result.append(store_team)
 
         return {
-            "merchant_name": merchant.business_name or merchant.brand_name,
+            "merchant_name": merchant.name,
             "owner_email": merchant.owner.email if merchant.owner else None,
             "stores": result,
             "total_members": sum(s["member_count"] for s in result),