feat(admin): 履约渠道接口与断代运维脚本

- 新增 /admin/fulfillment 待分类、指定渠道、规则 CRUD、问题队列、管道触发
- backfill-fulfillment-channel：438k 行分批回填，幂等可续跑
- finance-cutover-v2：默认 dry-run，--execute 才清理派生数据，禁止重复执行
- rebuild-after-cutover：按断代日重跑三条管道并生成期初分录

apps/backend/src/routes/admin.ts

@@ -7,6 +7,7 @@ import dashboardRouter from './admin/dashboard.js'
 import devMockRouter from './admin/dev-mock.js'
 import douyinMashidaRouter from './admin/douyin-mashida.js'
 import financeRouter from './admin/finance.js'
+import fulfillmentChannelRouter from './admin/fulfillment-channel.js'
 import financeLedgerRouter from './admin/finance-ledger.js'
 import fundRouter from './admin/fund.js'
 import filesRouter from './admin/files.js'
@@ -31,6 +32,7 @@ router.use(dashboardRouter)
 router.use(financeRouter)
 router.use(financeLedgerRouter)
 router.use(costCenterRouter)
+router.use(fulfillmentChannelRouter)
 router.use(fundRouter)
 router.use(usersRouter)
 router.use(rbacRouter)