Less verbose logging options

**is your feature request related to a problem? Please describe.**

By default logs are kind of all or nothing setup. With `-q` nothing is logged including stuff like user bans. (thus making `thank you for playing (see fileserver log and readme)` not helpful at all)

I tried to limit some logs with very wide `--lf-url`, but this only stops logging web requests. Entering a directory with images still generates a ton of thumbnail generating logs for example. This makes it quite hard to actually find useful logs when troubleshooting.

**Describe the idea / solution you'd like**

Global log level would be nice. At the very least implement this for the most "noisy" logs like access log and thumbnails. It would be nice if only failures were logged for these for example.

**Describe any alternatives you've considered**

I'm using `-q` right now, but that one is a bit too much, I would not mind some startup logs and such. I also appreciate some warning messages. The `--lf-url` can limit the access logs, but as far as I can tell this will also prevent failed access logs.

查看 copyparty 中的日志设置，可能位于主服务器模块或专用的日志配置中。确定访问日志和缩略图生成日志在哪里输出。目标是添加全局日志级别或针对嘈杂组件的单独控制，同时确保失败仍会被记录。检查现有的 flags（如 `-q` 和 `--lf-url`），以了解当前的日志结构。

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