```

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/ai_agent/routes.py

@@ -2,6 +2,7 @@ from fastapi import APIRouter, Depends
 from sqlalchemy.orm import Session
 
 from app.core.database import get_db
+from app.core.operation_guard import require_operations_enabled
 from app.core.security import ApiPrincipal, require_api_key
 from app.modules.audit.constants import AuditSource
 from app.modules.ai_agent.schemas import (
@@ -44,6 +45,7 @@ def invoke_openclaw_tool(
     db: Session = Depends(get_db),
     principal: ApiPrincipal = Depends(require_api_key),
 ) -> dict:
+    require_operations_enabled()
     return AIService(db).invoke_openclaw_tool(
         tool=payload.tool,
         action=payload.action,