feat: enhance Letzshop order import with EAN matching and stats

- Add historical order import with pagination support
- Add customer_locale, shipping_country_iso, billing_country_iso columns
- Add gtin/gtin_type columns to Product table for EAN matching
- Fix order stats to count all orders server-side (not just visible page)
- Add GraphQL introspection script with tracking workaround tests
- Enrich inventory units with EAN, MPN, SKU, product name
- Add LetzshopOrderStats schema for proper status counts

Migrations:
- a9a86cef6cca: Add locale and country fields to letzshop_orders
- cb88bc9b5f86: Add gtin columns to products table

🤖 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

@@ -227,3 +227,131 @@ class TestProductModel:
         assert info["brand"] == "SourceBrand"
         assert info["brand_overridden"] is False
         assert info["brand_source"] == "SourceBrand"
+
+
+@pytest.mark.unit
+@pytest.mark.database
+@pytest.mark.inventory
+class TestProductInventoryProperties:
+    """Test Product inventory properties including digital product handling."""
+
+    def test_physical_product_no_inventory_returns_zero(
+        self, db, test_vendor, test_marketplace_product
+    ):
+        """Test physical product with no inventory entries returns 0."""
+        # Ensure product is physical
+        test_marketplace_product.is_digital = False
+        db.commit()
+
+        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_digital is False
+        assert product.has_unlimited_inventory is False
+        assert product.total_inventory == 0
+        assert product.available_inventory == 0
+
+    def test_physical_product_with_inventory(
+        self, db, test_vendor, test_marketplace_product
+    ):
+        """Test physical product calculates inventory from entries."""
+        from models.database.inventory import Inventory
+
+        test_marketplace_product.is_digital = False
+        db.commit()
+
+        product = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+        )
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+
+        # Add inventory entries
+        inv1 = Inventory(
+            product_id=product.id,
+            vendor_id=test_vendor.id,
+            location="WAREHOUSE_A",
+            quantity=100,
+            reserved_quantity=10,
+        )
+        inv2 = Inventory(
+            product_id=product.id,
+            vendor_id=test_vendor.id,
+            location="WAREHOUSE_B",
+            quantity=50,
+            reserved_quantity=5,
+        )
+        db.add_all([inv1, inv2])
+        db.commit()
+        db.refresh(product)
+
+        assert product.has_unlimited_inventory is False
+        assert product.total_inventory == 150  # 100 + 50
+        assert product.available_inventory == 135  # (100-10) + (50-5)
+
+    def test_digital_product_has_unlimited_inventory(
+        self, db, test_vendor, test_marketplace_product
+    ):
+        """Test digital product returns unlimited inventory."""
+        test_marketplace_product.is_digital = True
+        db.commit()
+
+        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_digital is True
+        assert product.has_unlimited_inventory is True
+        assert product.total_inventory == Product.UNLIMITED_INVENTORY
+        assert product.available_inventory == Product.UNLIMITED_INVENTORY
+
+    def test_digital_product_ignores_inventory_entries(
+        self, db, test_vendor, test_marketplace_product
+    ):
+        """Test digital product returns unlimited even with inventory entries."""
+        from models.database.inventory import Inventory
+
+        test_marketplace_product.is_digital = True
+        db.commit()
+
+        product = Product(
+            vendor_id=test_vendor.id,
+            marketplace_product_id=test_marketplace_product.id,
+        )
+        db.add(product)
+        db.commit()
+        db.refresh(product)
+
+        # Add inventory entries (e.g., for license keys)
+        inv = Inventory(
+            product_id=product.id,
+            vendor_id=test_vendor.id,
+            location="DIGITAL_LICENSES",
+            quantity=10,
+            reserved_quantity=2,
+        )
+        db.add(inv)
+        db.commit()
+        db.refresh(product)
+
+        # Digital product should still return unlimited
+        assert product.has_unlimited_inventory is True
+        assert product.total_inventory == Product.UNLIMITED_INVENTORY
+        assert product.available_inventory == Product.UNLIMITED_INVENTORY
+
+    def test_unlimited_inventory_constant(self):
+        """Test UNLIMITED_INVENTORY constant value."""
+        assert Product.UNLIMITED_INVENTORY == 999999
+        # Should be large enough to never cause "insufficient inventory"
+        assert Product.UNLIMITED_INVENTORY > 100000