Fix first-login username flow

client/src/pages/Login.tsx

@@ -10,23 +10,41 @@ import { Target, Loader2 } from "lucide-react";
 export default function Login() {
   const [username, setUsername] = useState("");
   const [, setLocation] = useLocation();
-  const loginMutation = trpc.auth.loginWithUsername.useMutation({
-    onSuccess: (data) => {
-      toast.success(data.isNew ? `欢迎加入，${data.user.name}！` : `欢迎回来，${data.user.name}！`);
-      setLocation("/dashboard");
-    },
-    onError: (err) => {
-      toast.error("登录失败: " + err.message);
-    },
-  });
+  const utils = trpc.useUtils();
+  const loginMutation = trpc.auth.loginWithUsername.useMutation();
 
-  const handleLogin = (e: React.FormEvent) => {
+  const syncAuthenticatedUser = async (fallbackUser: Awaited<ReturnType<typeof loginMutation.mutateAsync>>["user"]) => {
+    // Seed the cache immediately so protected routes do not bounce back to /login.
+    utils.auth.me.setData(undefined, fallbackUser);
+
+    for (let attempt = 0; attempt < 3; attempt++) {
+      const user = await utils.auth.me.fetch();
+      if (user) {
+        utils.auth.me.setData(undefined, user);
+        return user;
+      }
+      await new Promise(resolve => window.setTimeout(resolve, 120 * (attempt + 1)));
+    }
+
+    return fallbackUser;
+  };
+
+  const handleLogin = async (e: React.FormEvent) => {
     e.preventDefault();
     if (!username.trim()) {
       toast.error("请输入用户名");
       return;
     }
-    loginMutation.mutate({ username: username.trim() });
+
+    try {
+      const data = await loginMutation.mutateAsync({ username: username.trim() });
+      const user = await syncAuthenticatedUser(data.user);
+      toast.success(data.isNew ? `欢迎加入，${user.name}！` : `欢迎回来，${user.name}！`);
+      setLocation("/dashboard");
+    } catch (err) {
+      const message = err instanceof Error ? err.message : "未知错误";
+      toast.error("登录失败: " + message);
+    }
   };
 
   return (