[Feature]能否只支持下载歌词，不下载歌曲

**思路和建议**

有些歌本地有了，只想下载个匹配的歌词，而不是和歌曲一起下载，这个可以吗

**参考代码**
提供代码参考

Look at the main download logic in the CLI entry point and the modules for each music service (e.g., netease.py, qq.py). Identify where song and lyric downloading are coupled. Add a flag or separate command to download only lyrics. Test by running the tool with the new option against a known song ID.

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