feat(mall): classic B2B2C PC storefront with fixed mock API layer

- Mock adapter implementing @vmall/shared ApiClient (localStorage-persisted
  cart/orders/invoices), runtime switch via mockApi flag (default on)
- Fixed bilingual mock catalog: 3-level categories, 24 products w/ SKUs,
  stores, brands, banners, floors, seckill/collective/integral, comments,
  coupons, addresses, seeded orders/shipments/invoices
- B2B2C mall shell: top bar, logo/search/cart header, dark nav + category
  mega-menu, value-prop footer, back-to-top; 1200px grid, #ca151e theme
- UI primitives replacing element-plus: carousel, pagination, breadcrumb,
  qty stepper, rating stars, modal, tabs, step bar, product card
- Pages: home floors, search (filters/sort/paging), goods detail (SKU
  picker, store rail, review tabs), cart -> checkout -> pay -> success,
  auth pages, user center (dashboard/orders/addresses/favorites/coupons/
  invoices), stores, seckill, collective, integral
- i18n split into per-domain locale modules (en+zh)
- OpenSpec change mall-pc-storefront-replica archived; all specs green

apps/mall/locales/cart.ts

@@ -0,0 +1,46 @@
+export default {
+  en: {
+    cart: {
+      title: "Shopping cart",
+      steps: { cart: "Cart", order: "Confirm order", payment: "Payment", complete: "Complete" },
+      empty: "Your cart is empty",
+      continueShopping: "Continue shopping",
+      selectAll: "Select all",
+      selectedCount: "{n} selected",
+      product: "Product",
+      spec: "Specification",
+      unitPrice: "Unit price",
+      quantity: "Quantity",
+      subtotal: "Subtotal",
+      actions: "Actions",
+      remove: "Remove",
+      shop: "Shop",
+      unknownStore: "Store",
+      checkout: "Checkout",
+      loadError: "Unable to load your cart.",
+      updateError: "Unable to update your cart.",
+    },
+  },
+  zh: {
+    cart: {
+      title: "购物车",
+      steps: { cart: "购物车", order: "确认订单", payment: "支付", complete: "完成" },
+      empty: "购物车还是空的",
+      continueShopping: "继续购物",
+      selectAll: "全选",
+      selectedCount: "已选 {n} 件",
+      product: "商品",
+      spec: "规格",
+      unitPrice: "单价",
+      quantity: "数量",
+      subtotal: "小计",
+      actions: "操作",
+      remove: "移除",
+      shop: "店铺",
+      unknownStore: "店铺",
+      checkout: "去结算",
+      loadError: "购物车加载失败，请稍后重试。",
+      updateError: "购物车更新失败，请稍后重试。",
+    },
+  },
+};