fix(order): align prisma schema with order service

prisma/schema.prisma

@@ -138,6 +138,11 @@ model Order {
   status         OrderStatus  @default(PENDING)
   totalAmount    Decimal      @db.Decimal(10, 2)
   addressSnapshot Json
+  // 客户端幂等键；同一用户重复提交时返回已有订单
+  requestId      String?
+  // 待付款订单的服务端截止时间
+  paymentExpiresAt DateTime?
+  paidAt         DateTime?
   // 关联的设计清单（R4 下单后 WCD 派单据此读取 designData）
   designListId   String?
   user           User         @relation(fields: [userId], references: [id])
@@ -151,6 +156,8 @@ model Order {
   @@index([userId])
   @@index([status])
   @@index([designListId])
+  @@index([paymentExpiresAt])
+  @@unique([userId, requestId])
 }
 
 enum OrderStatus {
@@ -160,6 +167,7 @@ enum OrderStatus {
   SHIPPED
   COMPLETED
   CANCELLED
+  PAYMENT_EXPIRED
 }
 
 model OrderItem {