feat(retention): 删除用户/Key 时保留历史记录，外键改 SET NULL 并添加名称快照

- Usage/RequestCandidate/VideoTask/Stats 等表的 user_id/api_key_id 外键从
  CASCADE 改为 SET NULL，删除用户或 Key 后历史记录不再丢失
- 各表添加 username/api_key_name 快照字段，删除后仍可追溯归属
- 新增 bulk_cleanup 模块，分批置空大表外键避免长事务锁
- 删除用户/Key 流程集成预清理步骤，先置空再删除
- 精简 candidate_builder 冗余 debug 日志
- 修复 proxy_nodes 启动日志 format 占位符错误（{} -> %s）
- 前端批量操作请求增加 5 分钟超时配置

frontend/src/api/endpoints/pool.ts

@@ -2,6 +2,8 @@ import client from '../client'
 import { dedupedRequest } from '@/utils/cache'
 import type { AllowedModels, ProxyConfig } from './types/provider'
 
+const POOL_BATCH_ACTION_TIMEOUT_MS = 5 * 60 * 1000
+
 export interface PoolKeyStatus {
   key_id: string
   key_name: string
@@ -212,13 +214,21 @@ export async function batchActionPoolKeys(
   providerId: string,
   body: PoolBatchAction,
 ): Promise<{ affected: number; message: string }> {
-  const response = await client.post(`/api/admin/pool/${providerId}/keys/batch-action`, body)
+  const response = await client.post(
+    `/api/admin/pool/${providerId}/keys/batch-action`,
+    body,
+    { timeout: POOL_BATCH_ACTION_TIMEOUT_MS },
+  )
   return response.data
 }
 
 export async function cleanupBannedPoolKeys(
   providerId: string,
 ): Promise<{ affected: number; message: string }> {
-  const response = await client.post(`/api/admin/pool/${providerId}/keys/cleanup-banned`)
+  const response = await client.post(
+    `/api/admin/pool/${providerId}/keys/cleanup-banned`,
+    undefined,
+    { timeout: POOL_BATCH_ACTION_TIMEOUT_MS },
+  )
   return response.data
 }