optimize: modify video.proto

[BaiZe1998]

修改pb文件：

1. 新增封面上传接口
2. base file 确认上传接口返回 url

Checklist

• [ ] Link to an issue if it really related.
• [ ] At least describe what this PR does.
• [ ] Use rebase to confirm that current branch doesn't conflict with main branch.
• [ ] Unit tests. At least do not reduce the unit test coverage.
• [ ] Checked and updated guidelines.md which used to describe how to build, deploy and use DouTok.