fix duplicate code in client.go

internal/upstream/client.go

@@ -253,7 +253,7 @@ body := map[string]interface{}{
 	req.Header.Set("Connection", "keep-alive")
 	req.Header.Set("Origin", "https://chat.z.ai")
 	req.Header.Set("Referer", fmt.Sprintf("https://chat.z.ai/c/%s", uuid.New().String()))
-	req.Header.Set("User-Agent", uarand.GetRandom())
+req.Header.Set("User-Agent", uarand.GetRandom())
 	if sess, err := auth.GetAnonymousSession(); err == nil {
 		var cookieStrs []string
 		for _, c := range sess.Cookies {
@@ -262,9 +262,6 @@ body := map[string]interface{}{
 		req.Header.Set("Cookie", strings.Join(cookieStrs, "; "))
 	}
 
-	client := proxy.GetHTTPClient()
-	}
-
 	client := proxy.GetHTTPClient()
 	resp, err := client.Do(req)
 	if err != nil {
@@ -274,6 +271,9 @@ body := map[string]interface{}{
 	return resp, targetModel, nil
 }
 
+	return resp, targetModel, nil
+}
+
 if sess, err := auth.GetAnonymousSession(); err == nil {
     var cookieStrs []string
     for _, c := range sess.Cookies {