#### What type of PR is this?
/area ui
/kind improvement
/milestone 2.21.x
#### What this PR does / why we need it:
This PR adds frontend support for checking whether an slug already exists when creating posts.
Note:
1. The current implementation isn’t perfect, some actions (like clicking the “Publish” button) don’t check for duplicate slug yet.
2. Slug checking in the user center might not be accurate, since it may not have permission to query all posts.
<img width="695" alt="image" src="https://github.com/user-attachments/assets/baa37a82-49c2-43be-a4d8-0e0f22a9d73b" />
#### Which issue(s) this PR fixes:
Fixes https://github.com/halo-dev/halo/issues/7615
Fixes https://github.com/halo-dev/halo/issues/3332
#### Special notes for your reviewer:
#### Does this PR introduce a user-facing change?
```release-note
创建文章时支持检查别名是否重复
```
#### What type of PR is this?
/area ui
/kind improvement
/milestone 2.17.x
#### What this PR does / why we need it:
重新组织和固定 UI 部分代码的 imports 导入，防止后续因为 imports 的顺序造成不必要的 diff。
基于：https://github.com/halo-dev/halo/pull/6151
#### Does this PR introduce a user-facing change?
```release-note
None
```
#### What type of PR is this?
/area ui
/kind improvement
/milestone 2.14.x
#### What this PR does / why we need it:
为 UC 端保存文章的操作添加重试机制，防止出现因为锁导致的保存失败问题。
#### Which issue(s) this PR fixes:
Fixes https://github.com/halo-dev/halo/issues/5474
#### Special notes for your reviewer:
需要多次尝试编辑文章，以及设置表单的保存功能。
#### Does this PR introduce a user-facing change?
```release-note
为 UC 端保存文章的操作添加重试机制，防止出现因为锁导致的保存失败问题。
```
Ryan Wang