Feature: tinyTikTok 基础接口

**Is your feature request related to a problem? Please describe.**
- 视频Feed流：支持所有用户刷抖音，视频按投稿时间倒序推出
- 视频投稿：支持登录用户自己拍视频投稿
- 个人主页：支持查看用户基本信息和投稿列表，注册用户流程简化

**Describe the solution you'd like**
- [ ] /douyin/feed/ - 视频流接口
- [ ] /douyin/user/register/ - 用户注册接口
- [ ] /douyin/user/login/ - 用户登录接口
- [ ] /douyin/user/ - 用户信息
- [ ] /douyin/publish/action/ - 视频投稿
- [ ] /douyin/publish/list/ - 发布列表

**Describe alternatives you've considered**
None.

**Additional context**
None.

Start by reviewing the repository entry points for the six requested endpoints: feed, registration, login, user information, video publishing, and publishing lists. Define the behavior and data flow for each endpoint before implementing them; the work is done when all listed interfaces support the described feed, authentication, profile, registration, and video-posting flows.

Written by the indexing model from the issue text.