```

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/routes.py

@@ -2,6 +2,7 @@ from fastapi import APIRouter, Depends, Query
 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.core.task_queue import enqueue_risk_event_generation
 from app.modules.risk.constants import RiskEventActionKey, RiskGenerationResultKey
@@ -94,6 +95,7 @@ def assign_risk_event(
     db: Session = Depends(get_db),
     principal: ApiPrincipal = Depends(require_api_key),
 ) -> dict:
+    require_operations_enabled()
     return RiskService(db).assign_event(
         event_id,
         assigned_to=payload.assigned_to,
@@ -109,6 +111,7 @@ def comment_risk_event(
     db: Session = Depends(get_db),
     principal: ApiPrincipal = Depends(require_api_key),
 ) -> dict:
+    require_operations_enabled()
     return RiskService(db).comment_event(
         event_id,
         comment=payload.comment,
@@ -124,6 +127,7 @@ def resolve_risk_event(
     db: Session = Depends(get_db),
     principal: ApiPrincipal = Depends(require_api_key),
 ) -> dict:
+    require_operations_enabled()
     return RiskService(db).resolve_event(
         event_id,
         comment=payload.comment,
@@ -139,12 +143,12 @@ def close_risk_event(
     db: Session = Depends(get_db),
     principal: ApiPrincipal = Depends(require_api_key),
 ) -> dict:
+    require_operations_enabled()
     return RiskService(db).close_event(
         event_id,
         closed_reason=payload.closed_reason,
         review_summary=payload.review_summary,
         actor=principal.actor,
-        approval_ticket_id=payload.approval_ticket_id,
     )
 
 
@@ -155,11 +159,11 @@ def reopen_risk_event(
     db: Session = Depends(get_db),
     principal: ApiPrincipal = Depends(require_api_key),
 ) -> dict:
+    require_operations_enabled()
     return RiskService(db).reopen_event(
         event_id,
         comment=payload.comment,
         actor=principal.actor,
-        approval_ticket_id=payload.approval_ticket_id,
     )
 
 
@@ -168,6 +172,7 @@ def generate_risk_events(
     db: Session = Depends(get_db),
     principal: ApiPrincipal = Depends(require_api_key),
 ) -> dict:
+    require_operations_enabled()
     return RiskService(db).generate_events(actor=principal.actor)
 
 
@@ -175,4 +180,5 @@ def generate_risk_events(
 def enqueue_risk_events(
     principal: ApiPrincipal = Depends(require_api_key),
 ) -> dict:
+    require_operations_enabled()
     return enqueue_risk_event_generation(actor=principal.actor)