修复(#134): 促销前端展示对齐 (expires_at / billing 补 promo_discount / 类型补字段)

Squash merge of fix/134-促销前端展示对齐 (4702dee).

HIF-79/HIF-113 落地后前端有三处对齐缺失：

- promo-info.tsx 仍读 promo.end_time，但后端 SubscribeDiscountPromo
  JSON 字段是 expires_at（×2 处）
- billing.tsx 缺 Promo Discount 行，PreOrderResponse 拿到 promo_discount
  时无处可渲染
- typings.d.ts: SubscribeDiscountPromo 缺 expires_at/rule_type,
  PreOrderResponse 缺 promo_discount

本次仅修字段对齐与展示行，不动业务逻辑、不动 OrderDetail 类型 (后端
当前未透出 promo_discount)。新增 billing.promoDiscount 中英文文案。

apps/user/public/assets/locales/en-US/subscribe.json

@@ -9,6 +9,7 @@
     "originalPrice": "Original Price (Monthly)",
     "price": "Price",
     "productDiscount": "Product Discount",
+    "promoDiscount": "Promo Discount",
     "total": "Total"
   },
   "buy": "Buy",

apps/user/public/assets/locales/zh-CN/subscribe.json

@@ -9,6 +9,7 @@
     "originalPrice": "原价（按月）",
     "price": "价格",
     "productDiscount": "商品折扣",
+    "promoDiscount": "促销优惠",
     "total": "总价"
   },
   "buy": "购买",

apps/user/src/sections/subscribe/billing.tsx

@@ -10,6 +10,7 @@ interface SubscribeBillingProps {
       unit_price: number;
       unit_time: string;
       subscribe_discount: number;
+      promo_discount: number;
       show_original_price?: boolean;
     }
   >;
@@ -66,6 +67,14 @@ export function SubscribeBilling({ order }: Readonly<SubscribeBillingProps>) {
             <Display type="currency" value={order?.discount} />
           </span>
         </li>
+        <li>
+          <span className="text-muted-foreground">
+            {t("billing.promoDiscount", "Promo Discount")}
+          </span>
+          <span>
+            <Display type="currency" value={order?.promo_discount} />
+          </span>
+        </li>
         <li>
           <span className="text-muted-foreground">
             {t("billing.couponDiscount", "Coupon Discount")}

apps/user/src/sections/subscribe/promo-info.tsx

@@ -18,10 +18,10 @@ export function PromoInfo({ discount }: Readonly<PromoInfoProps>) {
         <span className="font-medium">
           {promo.rule_name || t("promo.available", "Promo Available")}
         </span>
-        {promo.end_time && (
+        {promo.expires_at && (
           <span className="text-muted-foreground text-xs">
             {t("promo.validUntil", "Valid until")}:{" "}
-            {new Date(promo.end_time * 1000).toLocaleString()}
+            {new Date(promo.expires_at * 1000).toLocaleString()}
           </span>
         )}
       </div>

packages/ui/src/services/user/typings.d.ts

@@ -548,6 +548,7 @@ declare namespace API {
     price: number;
     amount: number;
     discount: number;
+    promo_discount: number;
     gift_amount: number;
     coupon: string;
     coupon_discount: number;
@@ -1024,8 +1025,9 @@ declare namespace API {
 
   type SubscribeDiscountPromo = {
     rule_name?: string;
+    rule_type?: string;
     promo_price: number;
-    end_time?: number;
+    expires_at?: number;
   };
 
   type SubscribeGroup = {