refactor: split database model tests into organized modules

Split the monolithic test_database_models.py into focused test modules:

Database model tests (tests/unit/models/database/):
- test_customer.py: Customer model and authentication tests
- test_inventory.py: Inventory model tests
- test_marketplace_import_job.py: Import job model tests
- test_marketplace_product.py: Marketplace product model tests
- test_order.py: Order and OrderItem model tests
- test_product.py: Product model tests
- test_team.py: Team invitation and membership tests
- test_user.py: User model tests
- test_vendor.py: Vendor model tests

Schema validation tests (tests/unit/models/schema/):
- test_auth.py: Auth schema validation tests
- test_customer.py: Customer schema validation tests
- test_inventory.py: Inventory schema validation tests
- test_marketplace_import_job.py: Import job schema tests
- test_order.py: Order schema validation tests
- test_product.py: Product schema validation tests

This improves test organization and makes it easier to find
and maintain tests for specific models.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/unit/models/database/test_product.py

@@ -0,0 +1,123 @@
+# tests/unit/models/database/test_product.py
+"""Unit tests for Product (vendor catalog) database model."""
+import pytest
+from sqlalchemy.exc import IntegrityError
+
+from models.database.product import Product
+
+
+@pytest.mark.unit
+@pytest.mark.database
+class TestProductModel:
+    """Test Product (vendor catalog) model."""
+
+    def test_product_creation(self, db, test_vendor, test_marketplace_product):
+        """Test Product model linking vendor catalog to marketplace product."""
+        product = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+            product_id="VENDOR_PROD_001",
+            price=89.99,
+            currency="EUR",
+            availability="in stock",
+            is_featured=True,
+            is_active=True,
+        )
+
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+
+        assert product.id is not None
+        assert product.vendor_id == test_vendor.id
+        assert product.marketplace_product_id == test_marketplace_product.id
+        assert product.price == 89.99
+        assert product.is_featured is True
+        assert product.vendor.vendor_code == test_vendor.vendor_code
+        assert product.marketplace_product.title == test_marketplace_product.title
+
+    def test_product_unique_per_vendor(self, db, test_vendor, test_marketplace_product):
+        """Test that same marketplace product can't be added twice to vendor catalog."""
+        product1 = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+            is_active=True,
+        )
+        db.add(product1)
+        db.commit()
+
+        # Same marketplace product to same vendor should fail
+        with pytest.raises(IntegrityError):
+            product2 = Product(
+                vendor_id=test_vendor.id,
+                marketplace_product_id=test_marketplace_product.id,
+                is_active=True,
+            )
+            db.add(product2)
+            db.commit()
+
+    def test_product_default_values(self, db, test_vendor, test_marketplace_product):
+        """Test Product model default values."""
+        product = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+        )
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+
+        assert product.is_active is True  # Default
+        assert product.is_featured is False  # Default
+        assert product.min_quantity == 1  # Default
+        assert product.display_order == 0  # Default
+
+    def test_product_vendor_override_fields(self, db, test_vendor, test_marketplace_product):
+        """Test Product model vendor-specific override fields."""
+        product = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+            product_id="CUSTOM_SKU_001",
+            price=49.99,
+            sale_price=39.99,
+            currency="USD",
+            availability="limited",
+            condition="new",
+        )
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+
+        assert product.product_id == "CUSTOM_SKU_001"
+        assert product.price == 49.99
+        assert product.sale_price == 39.99
+        assert product.currency == "USD"
+        assert product.availability == "limited"
+
+    def test_product_inventory_settings(self, db, test_vendor, test_marketplace_product):
+        """Test Product model inventory settings."""
+        product = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+            min_quantity=2,
+            max_quantity=10,
+        )
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+
+        assert product.min_quantity == 2
+        assert product.max_quantity == 10
+
+    def test_product_relationships(self, db, test_vendor, test_marketplace_product):
+        """Test Product relationships."""
+        product = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+        )
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+
+        assert product.vendor is not None
+        assert product.marketplace_product is not None
+        assert product.inventory_entries == []  # No inventory yet