```

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/risk/schemas.py

@@ -21,9 +21,7 @@ class RiskResolveRequest(BaseModel):
 class RiskCloseRequest(BaseModel):
     closed_reason: str = Field(..., min_length=1)
     review_summary: str | None = None
-    approval_ticket_id: str | None = None
 
 
 class RiskReopenRequest(BaseModel):
     comment: str | None = None
-    approval_ticket_id: str | None = None