test(backend): update auth and employee service tests

- tests/test_auth_service.py: update auth service tests
- tests/test_employee_service.py: update employee service tests

server/tests/test_employee_service.py

@@ -118,6 +118,23 @@ def test_disable_employee_marks_status_and_logs_change() -> None:
         assert any(item.action == "停用员工账号" for item in updated.history)
 
 
+def test_enable_employee_restores_status_and_logs_change() -> None:
+    with build_session() as db:
+        service = EmployeeService(db)
+        employee = next(item for item in service.list_employees() if item.status != "停用")
+        service.disable_employee(employee.id)
+
+        updated = service.enable_employee(employee.id)
+
+        persisted = db.get(Employee, employee.id)
+
+        assert updated.status == "在职"
+        assert updated.statusTone == "success"
+        assert persisted is not None
+        assert persisted.employment_status == "在职"
+        assert any(item.action == "启用员工账号" for item in updated.history)
+
+
 def test_update_employee_rejects_invalid_date_format() -> None:
     with build_session() as db:
         service = EmployeeService(db)