test: update tests for multi-language translation support

- Update marketplace_product_fixtures to create translations
- Update test_marketplace_product.py for translation-based titles
- Update test_product.py for effective property tests
- Update test_order.py to use get_title() method
- Add comprehensive CSV processor tests for translations
- Update stats service tests for new flat response structure
- Fix product schema tests with required marketplace_product_id field
- Add helper function create_marketplace_product_with_translation()

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/unit/models/database/test_product.py

@@ -16,7 +16,7 @@ class TestProductModel:
         product = Product(
             vendor_id=test_vendor.id,
             marketplace_product_id=test_marketplace_product.id,
-            product_id="VENDOR_PROD_001",
+            vendor_sku="VENDOR_PROD_001",
             price=89.99,
             currency="EUR",
             availability="in stock",
@@ -34,7 +34,11 @@ class TestProductModel:
         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
+        # Use get_title() method instead of .title attribute
+        assert (
+            product.marketplace_product.get_title("en")
+            == test_marketplace_product.get_title("en")
+        )
 
     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."""
@@ -76,7 +80,7 @@ class TestProductModel:
         product = Product(
             vendor_id=test_vendor.id,
             marketplace_product_id=test_marketplace_product.id,
-            product_id="CUSTOM_SKU_001",
+            vendor_sku="CUSTOM_SKU_001",
             price=49.99,
             sale_price=39.99,
             currency="USD",
@@ -87,7 +91,7 @@ class TestProductModel:
         db.commit()
         db.refresh(product)
 
-        assert product.product_id == "CUSTOM_SKU_001"
+        assert product.vendor_sku == "CUSTOM_SKU_001"
         assert product.price == 49.99
         assert product.sale_price == 39.99
         assert product.currency == "USD"
@@ -121,3 +125,99 @@ class TestProductModel:
         assert product.vendor is not None
         assert product.marketplace_product is not None
         assert product.inventory_entries == []  # No inventory yet
+
+    def test_product_effective_properties(self, db, test_vendor, test_marketplace_product):
+        """Test Product effective properties with override pattern."""
+        # First, set some values on the marketplace product
+        test_marketplace_product.price_numeric = 100.00
+        test_marketplace_product.brand = "SourceBrand"
+        db.commit()
+        db.refresh(test_marketplace_product)
+
+        # Create product without overrides
+        product = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+        )
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+
+        # Should inherit from marketplace product
+        assert product.effective_price == 100.00
+        assert product.effective_brand == "SourceBrand"
+
+        # Now override the price
+        product.price = 89.99
+        db.commit()
+        db.refresh(product)
+
+        # Should use the override
+        assert product.effective_price == 89.99
+        # Brand still inherited
+        assert product.effective_brand == "SourceBrand"
+
+    def test_product_reset_to_source(self, db, test_vendor, test_marketplace_product):
+        """Test reset_to_source methods."""
+        # Set up marketplace product values
+        test_marketplace_product.price_numeric = 100.00
+        test_marketplace_product.brand = "SourceBrand"
+        db.commit()
+
+        # Create product with overrides
+        product = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+            price=89.99,
+            brand="OverrideBrand",
+        )
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+
+        assert product.effective_price == 89.99
+        assert product.effective_brand == "OverrideBrand"
+
+        # Reset price to source
+        product.reset_field_to_source("price")
+        db.commit()
+        db.refresh(product)
+
+        assert product.price is None
+        assert product.effective_price == 100.00  # Now inherits
+
+        # Reset all fields
+        product.reset_all_to_source()
+        db.commit()
+        db.refresh(product)
+
+        assert product.brand is None
+        assert product.effective_brand == "SourceBrand"  # Now inherits
+
+    def test_product_get_override_info(self, db, test_vendor, test_marketplace_product):
+        """Test get_override_info method."""
+        test_marketplace_product.price_numeric = 100.00
+        test_marketplace_product.brand = "SourceBrand"
+        db.commit()
+
+        product = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+            price=89.99,  # Override
+            # brand not set - will inherit
+        )
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+
+        info = product.get_override_info()
+
+        # Price is overridden
+        assert info["price"] == 89.99
+        assert info["price_overridden"] is True
+        assert info["price_source"] == 100.00
+
+        # Brand is inherited
+        assert info["brand"] == "SourceBrand"
+        assert info["brand_overridden"] is False
+        assert info["brand_source"] == "SourceBrand"