fix(miniprogram): 退出登录后刷新仍保持登录态

根因：logout 清除 storage 期间并发请求触发 tryRefreshToken 写回新 token
修复：添加 isLoggingOut 标记，logout 时先标记阻止 token 刷新竞态

apps/miniprogram/src/services/request.ts

@@ -30,8 +30,18 @@ async function getHeaders(): Promise<Record<string, string>> {
 
 // --- Token refresh deduplication ---
 let refreshPromise: Promise<boolean> | null = null;
+let isLoggingOut = false;
+
+export function markLoggingOut(): void {
+  isLoggingOut = true;
+}
+
+export function clearLoggingOut(): void {
+  isLoggingOut = false;
+}
 
 async function tryRefreshToken(): Promise<boolean> {
+  if (isLoggingOut) return false;
   if (refreshPromise) return refreshPromise;
   refreshPromise = doRefresh();
   refreshPromise.finally(() => { refreshPromise = null; });