feat(buyer): 增强商品详情与支付逻辑

- 引入 buyerLogin 工具，优化商品详情页的链接跳转逻辑，确保未登录用户能正确重定向到登录页面
- 更新商品 SKU 详情 API，支持未登录状态下的访问
- 修改支付 API，新增 skipMessage 参数以控制支付提示信息
- 改进商品列表与支付页面的用户体验，确保更流畅的操作流程
- 规范化商品类型与库存提示，提升用户体验

buyer/src/utils/buyerLogin.js

@@ -0,0 +1,59 @@
+/**
+ * 买家端登录态与商品详情跳转校验
+ *
+ * @author Mike
+ * @date 2026-08-05
+ */
+import storage from "@/plugins/storage";
+
+export function isBuyerLoggedIn() {
+  const rawUserInfo = storage.getItem("userInfo");
+  if (rawUserInfo) {
+    try {
+      return !!JSON.parse(rawUserInfo).username;
+    } catch {
+      return false;
+    }
+  }
+  return !!storage.getItem("accessToken");
+}
+
+export function parseInternalLink(url) {
+  const [path, search = ""] = url.split("?");
+  const query = {};
+  if (search) {
+    new URLSearchParams(search).forEach((value, key) => {
+      query[key] = value;
+    });
+  }
+  return { path, query };
+}
+
+export function isGoodsDetailPath(path) {
+  return path === "/goodsDetail";
+}
+
+export function redirectToLogin(router, location) {
+  router.push({
+    path: "/login",
+    query: {
+      rePath: location.path,
+      query: JSON.stringify(location.query || {}),
+    },
+  });
+}
+
+/** 内部链接跳转；访问商品详情前校验登录（首页装修、列表等共用） */
+export function openLink(url, router) {
+  if (!url) return;
+  if (url.charAt(0) !== "/") {
+    window.open(url, "_blank");
+    return;
+  }
+  const location = parseInternalLink(url);
+  if (!isBuyerLoggedIn() && isGoodsDetailPath(location.path)) {
+    redirectToLogin(router, location);
+    return;
+  }
+  window.open(router.resolve(url).href, "_blank");
+}