refactor: 将多个 fmt.Println 日志替换为 log.Printf，以统一日志输出格式并提升可读性

util/url.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"log"
 	"net/url"
 	"os"
 	"path"
@@ -90,7 +91,7 @@ func DownloadFile(urlStr string, dirPath string, skipExist bool) (filepath strin
 	var maxRetry = 100
 	var retry = 0
 	for err = client.Do(req, resp); err != nil && retry < maxRetry; err = client.Do(req, resp) {
-		fmt.Printf("下载失败，正在重试... 错误: %v\n", err)
+		log.Printf("下载失败，正在重试... 错误: %v\n", err)
 		retry++
 	}
 	if err != nil {