fix: add bin_location to inventory fixtures and service

- Add warehouse and bin_location fields to test fixtures
- Update InventoryService to include warehouse/bin_location when creating entries
- Fix all Inventory model instantiations in tests to include required fields
- All 119 inventory tests now pass

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

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

tests/fixtures/vendor_fixtures.py

@@ -191,6 +191,8 @@ def test_inventory(db, test_product):
     inventory = Inventory(
         product_id=test_product.id,
         vendor_id=test_product.vendor_id,
+        warehouse="strassen",
+        bin_location=f"SA-10-{unique_id[:2]}",
         location=f"WAREHOUSE_A_{unique_id}",
         quantity=100,
         reserved_quantity=10,
@@ -208,7 +210,10 @@ def multiple_inventory_entries(db, multiple_products, test_vendor):
     inventory_entries = []
     for i, product in enumerate(multiple_products):
         inventory = Inventory(
+            product_id=product.id,
             gtin=product.gtin,
+            warehouse="strassen",
+            bin_location=f"SA-{i:02d}-01",
             location=f"LOC_{i}",
             quantity=10 + (i * 5),
             reserved_quantity=i,