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/user.ts

@@ -77,6 +77,8 @@ export default {
       removeFavorite: "Remove favorite",
       enterStore: "Enter store",
       noFavoriteStores: "No favorite stores yet.",
+      favoriteLoadFailed: "Unable to load favorites",
+      favoriteRemoveFailed: "Unable to remove favorite",
       couponsTitle: "My coupons",
       couponTitle: "Coupon",
       amount: "Amount",
@@ -174,6 +176,8 @@ export default {
       removeFavorite: "取消收藏",
       enterStore: "进入店铺",
       noFavoriteStores: "暂无关注店铺。",
+      favoriteLoadFailed: "收藏加载失败",
+      favoriteRemoveFailed: "取消收藏失败",
       couponsTitle: "我的优惠券",
       couponTitle: "优惠券",
       amount: "优惠金额",