[Feature] The function of obtaining the index and content of the score sheet in real time using a custom link

### Is your feature request related to a problem?

EN：
No, it's just my personal feeling. Maybe it's a feature _that_ is more friendly to users who don't have enough storage on their devices but have cloud storage and VPS.It's not, it's just my personal feeling that maybe it's a feature that is more friendly to users with insufficient device storage but vps and cloud storage are available.

ZH：
不，这只是我的个人感受。也许这是一个功能，对于那些在设备上没有足够存储空间但拥有云存储和虚拟专用网络（VPS）的用户来说更为友好。

### Describe the feature

EN：
The final result (from the idea of non-IT people): Give the webdav link to astrodx, so that it can automatically read the levels index.json in the web disk and cache it locally to display the name of the spectrum (I don't think it's possible to display pictures, Because it seems like all the sheet music diagrams use the same can also set this function as "power generation project."art, adx will ask you to choose whether to "cache to local" or "delete directly after playing". Next, adx downloads the corresponding index folder from webdav to the local levels file on the device (or downloads the corresponding index .zip and extracts it to levels).

Side note: I think if you are willing to accept this proposal, you might as wellcan also set this function as a "buy-out power project".

ZH：
最终实现结果(来自非 IT 人士的想法)：把 webdav 的链接给 astrodx，让它自动读取网盘上 levels 中的 index.json 缓存至本地显示谱面名称（显示图片我觉得是做不到的，因为貌似所有谱面的图都用的一个名字），用户手动选择游玩的谱面，点开始后 adx 会要求选择“缓存至本地”或“游玩后直接删除”，接下来 adx 从 webdav 下载对应索引的文件夹至设备本地的 levels 文件（活着下载对应索引的.zip 解压至 levels）。

题外话：我觉得如果您愿意接受这个提议的话，也不妨将此功能设为“买断制的发电项目”。

### Reason for adding

EN：
As a maimai enthusiast and a student, I don't have much time to play maimai in the arcade, so I rely heavily on adx for playing the charts, and on the day of the feature, I was integrating the charts from 1.66Circle... The "fantasy" I described above may be my wish.

ZH：
作为舞萌爱好者和一名学生，我在游戏厅上没太多时间玩舞萌，所以我非常依赖adx来玩谱面，而在这个feature提出的当天，我正在整合1.66Circle的谱面文件......以描述的“幻想”是我的愿望。

### Example(s)

_No response_

### Additional context

_No response_

The issue describes a feature for streaming score sheets from a WebDAV link. Start by examining the codebase for how levels/index.json is currently loaded and cached locally. Look for file I/O operations and network handling. Determine what 'done' looks like by understanding the integration points for WebDAV, local caching, and user prompts for cache/delete options.

Scritto dal modello di indicizzazione a partire dal testo della issue.