fix: update test files to match actual backend schemas and endpoints

backend/tests/test_items.py

@@ -12,7 +12,7 @@ class TestItemCRUD:
             json={
                 "name": "Test Item",
                 "category": "Electronics",
-                "item_type": "Component",
+                "type": "Component",
                 "quantity": 10,
                 "barcode": "123456789",
                 "part_number": "PN-12345"
@@ -141,7 +141,7 @@ class TestItemValidation:
             json={
                 "name": "Item2",
                 "category": "B",
-                "item_type": "Type",
+                "type": "Type",
                 "quantity": 5,
                 "barcode": "UNIQUE123",
                 "part_number": "PN2"
@@ -156,7 +156,7 @@ class TestItemValidation:
             json={
                 "name": "Test",
                 "category": "A",
-                "item_type": "Type",
+                "type": "Type",
                 "quantity": -5,
                 "barcode": "123",
                 "part_number": "PN"