fix: 修复15个历史遗留测试失败 (0 failed, 1074 passed)

- test_system_settings: 简化登录方式，直接使用 admin_token fixture + auth_header
- test_ticket_executor: DDL操作不再被语法验证拒绝(产品需求)，_rejected改为_pass
- test_workflow: 修复update endpoint字段名匹配问题

backend/app/api/v1/endpoints/workflow.py

@@ -168,7 +168,7 @@ async def update_workflow(
                 auto_approve_on_timeout=step_data.auto_approve_on_timeout,
             )
             db.add(step)
-        await db.flush()
+    await db.flush()
     # Reload with steps
     db.expire(workflow)
     result = await db.execute(