```

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/observability/constants.py

@@ -9,7 +9,6 @@ class ObservabilityKey(StrEnum):
     REDIS = "redis"
     EVENTS = "events"
     WORKFLOWS = "workflows"
-    WRITEBACKS = "writebacks"
 
 
 class ObservabilityStatus(StrEnum):
@@ -24,4 +23,3 @@ class ObservabilityMetricKey(StrEnum):
     PENDING = "pending"
     FAILED = "failed"
     RUNNING = "running"
-    DISABLED = "disabled"

app/modules/observability/service.py

@@ -13,8 +13,6 @@ from app.modules.observability.constants import (
 )
 from app.modules.workflows.constants import WorkflowStatus
 from app.modules.workflows.service import WorkflowService
-from app.modules.writebacks.constants import WritebackStatus
-from app.modules.writebacks.service import WritebackService
 
 
 class ObservabilityService:
@@ -32,7 +30,6 @@ class ObservabilityService:
             ObservabilityKey.REDIS: self._redis_check(),
             ObservabilityKey.EVENTS: self._events_check(),
             ObservabilityKey.WORKFLOWS: self._workflows_check(),
-            ObservabilityKey.WRITEBACKS: self._writebacks_check(),
         }
         degraded = any(
             item[ObservabilityKey.STATUS]
@@ -51,7 +48,6 @@ class ObservabilityService:
             ObservabilityKey.METRICS: {
                 ObservabilityKey.EVENTS: EventService(self.db).count_by_status(),
                 ObservabilityKey.WORKFLOWS: WorkflowService(self.db).count_by_status(),
-                ObservabilityKey.WRITEBACKS: WritebackService(self.db).count_by_status(),
             }
         }
 
@@ -101,14 +97,3 @@ class ObservabilityService:
             ObservabilityMetricKey.RUNNING: counts.get(WorkflowStatus.RUNNING, 0),
             ObservabilityMetricKey.FAILED: failed,
         }
-
-    def _writebacks_check(self) -> dict[str, Any]:
-        counts = WritebackService(self.db).count_by_status()
-        failed = counts.get(WritebackStatus.FAILED, 0)
-        return {
-            ObservabilityKey.STATUS: (
-                ObservabilityStatus.DEGRADED if failed else ObservabilityStatus.OK
-            ),
-            ObservabilityMetricKey.DISABLED: counts.get(WritebackStatus.DISABLED, 0),
-            ObservabilityMetricKey.FAILED: failed,
-        }