Support providing Console/UC UI extensions (main.js and style.css) from themes

[ruibaby]

Environment

Your current Halo version: 2.24

Details

Currently, only plugins can provide Console/User Center UI extensions (main.js and style.css) via the console/ directory in the plugin JAR. Themes are limited to providing Thymeleaf templates and static assets for the front-end site.

It would be helpful if themes could also provide main.js and style.css to extend the Console and User Center UI. This would allow themes to contribute custom settings pages, extension points, routes, and components — just like plugins do today.

Use cases include:

• Themes providing richer configuration UI in the Console (e.g., live preview, drag-and-drop layout settings)
• Themes contributing custom tabs or panels in the Console theme detail page
• Themes extending the User Center with theme-specific features
• Themes wanting to extend the editor with custom blocks without having to create a separate plugin

Additional information

None

[w-flac]

我愿称之为最强issues！ 此举可极大减少主题开发者对于插件后端扩展的依赖！！！！

[ruibaby]

已经在 #10053 和 #10057 中完成