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/package.json

@@ -10,7 +10,9 @@
     "db:migrate:create": "tsx scripts/create-migration.ts",
     "db:migrate:status": "tsx scripts/migration-status.ts",
     "finance:sync": "tsx scripts/sync-cost-finance.ts",
+    "finance:rebuild-cutover": "tsx scripts/rebuild-after-cutover.ts",
     "fulfillment:backfill": "tsx scripts/backfill-fulfillment-mode.ts",
+    "fulfillment:backfill-channel": "tsx scripts/backfill-fulfillment-channel.ts",
     "revenue:backfill": "tsx scripts/backfill-revenue-basis.ts",
     "cost-exceptions:archive": "tsx scripts/archive-cost-exceptions.ts",
     "storage:migrate": "tsx scripts/migrate-storage.ts",