Add WeChat login binding gate and context-aware auth UX.

Stop auto-creating duplicate accounts on OAuth, add bind-or-register gate,
PC scan login, mobile open-in-WeChat guide, and fix localhost session cookies.

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

src/utils/wechat.ts

@@ -3,6 +3,58 @@ export function isWechatBrowser(userAgent = navigator.userAgent) {
   return /MicroMessenger/i.test(ua) || /WindowsWechat/i.test(ua);
 }
 
+export function isMobileBrowser(userAgent = navigator.userAgent) {
+  return /Android|iPhone|iPad|iPod|Mobile/i.test(userAgent || '');
+}
+
+export function isIosBrowser(userAgent = navigator.userAgent) {
+  return /iPhone|iPad|iPod/i.test(userAgent || '');
+}
+
+/** 手机外部浏览器（Safari / Chrome 等），不在微信内 */
+export function isMobileExternalBrowser(options?: {
+  userAgent?: string;
+  search?: string;
+  serverInWechat?: boolean;
+}) {
+  return isMobileBrowser(options?.userAgent) && !isWechatContext(options);
+}
+
+/** 构建「在微信中打开」后应访问的链接（带上 from=wechat 以展示一键登录） */
+export function buildPageUrlForWechatOpen(
+  search = window.location.search,
+  pathname = window.location.pathname,
+) {
+  const params = new URLSearchParams(search);
+  params.set('from', 'wechat');
+  if (!params.get('utm_source')) params.set('utm_source', 'wechat');
+  const query = params.toString();
+  return `${window.location.origin}${pathname}${query ? `?${query}` : ''}${window.location.hash}`;
+}
+
+export async function copyWechatOpenLink(): Promise<boolean> {
+  const url = buildPageUrlForWechatOpen();
+  try {
+    await navigator.clipboard.writeText(url);
+    return true;
+  } catch {
+    try {
+      const input = document.createElement('textarea');
+      input.value = url;
+      input.setAttribute('readonly', 'true');
+      input.style.position = 'fixed';
+      input.style.left = '-9999px';
+      document.body.appendChild(input);
+      input.select();
+      const ok = document.execCommand('copy');
+      document.body.removeChild(input);
+      return ok;
+    } catch {
+      return false;
+    }
+  }
+}
+
 /** 从服务号链接进入时带的参数（即使 UA 识别失败也展示微信登录） */
 export function isWechatEntryUrl(search = window.location.search) {
   const params = new URLSearchParams(search);
@@ -26,6 +78,8 @@ export function buildWechatAuthorizeUrl(options?: {
   utmSource?: string;
   utmMedium?: string;
   utmCampaign?: string;
+  intent?: 'login' | 'register' | 'bind';
+  authMode?: 'mp' | 'open';
 }) {
   const params = new URLSearchParams();
   const returnTo =
@@ -37,10 +91,23 @@ export function buildWechatAuthorizeUrl(options?: {
   if (options?.utmSource) params.set('utm_source', options.utmSource);
   if (options?.utmMedium) params.set('utm_medium', options.utmMedium);
   if (options?.utmCampaign) params.set('utm_campaign', options.utmCampaign);
+  if (options?.intent) params.set('intent', options.intent);
+  if (options?.authMode) params.set('auth_mode', options.authMode);
   const query = params.toString();
   return query ? `/auth/wechat/authorize?${query}` : '/auth/wechat/authorize';
 }
 
+export function readWechatPendingToken(): string | null {
+  const params = new URLSearchParams(window.location.search);
+  const pending = params.get('wechat_pending');
+  if (!pending) return null;
+  params.delete('wechat_pending');
+  const nextSearch = params.toString();
+  const nextUrl = `${window.location.pathname}${nextSearch ? `?${nextSearch}` : ''}${window.location.hash}`;
+  window.history.replaceState({}, '', nextUrl);
+  return pending;
+}
+
 export function readWechatAuthError(): string | null {
   const params = new URLSearchParams(window.location.search);
   const error = params.get('wechat_error');