fix: 移除云端函数HTTP客户端硬编码代理

- 将硬编码的代理地址改为从环境变量读取
- 使用 http.ProxyFromEnvironment 让代理配置更灵活
- 服务器环境不设置代理环境变量即可直连

backend/internal/utils/httputil/client.go

@@ -32,14 +32,14 @@ func NewHTTPClient(timeout time.Duration) *HTTPClient {
 		timeout = DefaultTimeout
 	}
 
-	proxyURL, _ := url.Parse("http://127.0.0.1:10809")
+	transport := &http.Transport{
+		Proxy: http.ProxyFromEnvironment,
+	}
 
 	return &HTTPClient{
 		client: &http.Client{
-			Timeout: timeout,
-			Transport: &http.Transport{
-				Proxy: http.ProxyURL(proxyURL),
-			},
+			Timeout:   timeout,
+			Transport: transport,
 		},
 		timeout: timeout,
 	}