feat: persist customer product and shop favorites through the live API

Replace mall fixture favorites with customer-scoped endpoints, and send signed-out shoppers back to the page they left after sign-in.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/mall/locales/product.ts

@@ -24,6 +24,8 @@ export default {
       addedCart: "Added to cart",
       favorite: "Favorite",
       unfavorite: "Unfavorite",
+      favoriteFailed: "Unable to update favorite",
+      favoriteLoadFailed: "Unable to load favorite state",
       noStock: "Out of stock",
       unavailable: "This combination is unavailable",
       store: "Store",
@@ -72,6 +74,8 @@ export default {
       addedCart: "已加入购物车",
       favorite: "收藏",
       unfavorite: "取消收藏",
+      favoriteFailed: "收藏更新失败",
+      favoriteLoadFailed: "无法加载收藏状态",
       noStock: "暂时缺货",
       unavailable: "该规格暂不可用",
       store: "店铺",