fix(main.go): use minSpeed variable for speed comparison

- replace hardcoded speed threshold with minSpeed variable

Author: faceair

main.go

@@ -94,7 +94,7 @@ func printResults(results []*speedtester.Result) {
 		speed := float64(result.DownloadSpeed) / (1024 * 1024) // 转换为 MB/s
 		if speedStr == "0.00B/s" {
 			color = colorRed
-		} else if speed >= 10 {
+		} else if speed >= *minSpeed {
 			color = colorGreen
 		}