feat: Enhance models and README with additional features and improvements

- Updated README to include KodBox in project vision.
- Added model descriptions for clarity in Download, File, Folder, Group, Node, Order, Policy, Redeem, Report, Request, Response, Setting, Share, SourceLink, StoragePack, Tag, Task, User, and WebDAV.
- Changed optional fields from Optional[...] to the new union type syntax (e.g., str | None).
- Improved foreign key references in models for consistency.
- Refactored relationships in models to use singular forms where appropriate.
- Updated login service to reflect changes in request model types.

README.md

@@ -8,7 +8,7 @@
 
 本来此项目并没有这么快开始，但由于我曾经使用过的某个类似产品的作者吃相实在难看，故决定自己实现一个。
 
-此项目的愿景是集百家之长（Cloudreve + Alist + FnOS）。你也可以考虑付费支持我们的发展 -> `DiskNext Pro`.
+此项目的愿景是集百家之长（Cloudreve + Alist + FnOS + KodBox）。你也可以考虑付费支持我们的发展 -> `DiskNext Pro`.
 
 目前正处于 `OMEGA` 实验阶段，比 `Alpha` 版还更早期，仅供测试。
 
@@ -25,12 +25,12 @@
 - 在线预览/编辑多种文件，包括但不限于视频、图片、音频、PDF、ePub、Office、Markdown、图表等
 - 自定义主题色、深浅色主题、PWA、i18n
 
-## :alembic: 技术栈
+## ⚗️ 技术栈
 
 * [Python](https://www.python.org/) + [FastAPI](https://fastapi.tiangolo.com/)
 
 <!-- * [React](https://github.com/facebook/react) + [Redux](https://github.com/reduxjs/redux) + [Material-UI](https://github.com/mui-org/material-ui) -->
 
-## :scroll: 许可证
+## 📜 许可证
 
-GPL V3
+GPL V3