feat(finance): 支持代录指定客服账户，并上线影子总账/对账/关账/快手平台退款

- 人工确认履约：管理员/财务/运营可传 fundAccountId / creditOwnerAdminUserId
  指定客服备用金/积分账户；客服仍强制本人账户
- 新增迁移 112：finance_accounts / journal_entries / journal_lines /
  periods / reconciliations / reconciliation_items，种子 11 个科目
- 影子总账：销售事实按日生成收入/退款/成本凭证，支持手工凭证、试算平衡；
  不接管钱包余额；总账同步接入定时任务与退款重算
- 期间关账/反关账：关账先补凭证并校验试算平衡，closed 期间禁止新增凭证
- 平台对账：JSON 账单导入，按 provider + platform_order_id 匹配订单/退款，
  标记 matched/amount_mismatch/missing_order/missing_refund/duplicate
- 平台退款：快手行业（91）同意退款 API 接入，成功后落 source=platform；
  抖音/拼多多返回 501，保留手工退款
- 新增后台「财务 → 总账与对账」页面（总账/期间/对账三个 Tab）
- 集成测试扩展到代录、总账平衡、关账阻断、手工凭证、对账匹配

验证：backend check 844（840 pass / 4 skip）；frontend check 172 + build；
迁移 112 在 scratch 库全量执行并重跑幂等；本地生产副本已升级到 112，
销售事实同步 56 条凭证，借贷合计 1,885,351,864 = 1,885,351,864。

apps/backend/src/routes/admin/orders.ts

@@ -8,6 +8,7 @@ import {
 } from '../../services/admin/write/order-actions.js'
 import {
   createManualRefund,
+  createPlatformRefund,
   listOrderRefunds,
   voidOrderRefund,
 } from '../../services/finance/order-refund-service.js'
@@ -103,6 +104,42 @@ router.get(
   ),
 )
 
+router.post(
+  '/orders/:orderId/refunds/platform',
+  requireAdminPermission('finance.config'),
+  createJsonHandler(
+    (req) => {
+      const body = req.body as Record<string, unknown>
+      return createPlatformRefund(
+        {
+          orderId: String((req.params as AdminOrderRouteParams).orderId || ''),
+          orderItemId: body?.orderItemId as string | undefined,
+          amountFen: body?.amountFen as string | undefined,
+          platformRefundId: String(body?.platformRefundId || ''),
+          reason: body?.reason as string | undefined,
+          note: body?.note as string | undefined,
+          refundedAt: body?.refundedAt as string | undefined,
+          sellerId: body?.sellerId as string | undefined,
+          refundHandingWay: body?.refundHandingWay,
+          desc: body?.desc as string | undefined,
+        },
+        req.adminSession || null,
+      )
+    },
+    {
+      successMessage: '平台退款已提交并登记',
+      errorMessage: '平台退款失败',
+      scope: '[admin/orders/:orderId/refunds/platform]',
+      audit: (req, data) => ({
+        action: 'order_platform_refund_created',
+        targetType: 'order',
+        targetId: String((req.params as AdminOrderRouteParams).orderId || ''),
+        data: data && typeof data === 'object' ? (data as Record<string, unknown>) : {},
+      }),
+    },
+  ),
+)
+
 router.post(
   '/orders/:orderId/refunds',
   requireAdminPermission('finance.config'),