```

refactor: 移除审批和回写功能模块

移除了整个审批(approvals)和官方回写(writebacks)功能模块，
包括相关模型、路由、服务和配置项。更新了数据库迁移文件，
删除了相关的审批请求表和官方回写运行表。同时从API路由器中
移除了相应的路由，并调整了安全常量和字段验证器以匹配变更。
```

app/modules/workflows/constants.py

@@ -3,11 +3,9 @@ from enum import StrEnum
 
 class WorkflowType(StrEnum):
     RISK_EVENT_REVIEW = "risk_event_review"
-    OFFICIAL_WRITEBACK = "official_writeback"
 
 
 class WorkflowStatus(StrEnum):
-    WAITING_APPROVAL = "waiting_approval"
     WAITING_REVIEW = "waiting_review"
     RUNNING = "running"
     BLOCKED = "blocked"