Enable/Disable Templates

### The required feature described as a wish

After working more extensively with ACS, I’ve noticed several missing features that are necessary for effective template management.

When uploading a modified version of an existing template (for example, Rocky9), we are forced to give it a new name rather than following our established naming scheme, in order to avoid confusion with the old version. We also cannot simply delete the old template, as it is already in use by multiple production instances.

As a result, an Enable/Disable feature is needed. This would allow older templates to be disabled while keeping updated or approved templates active. Existing instances would continue running on the old templates, while new instances would be created using the enabled, updated ones.

未指定任何檔案、測試或進入點；先追蹤 ACS 範本上傳和執行個體建立流程。定義並驗證啟用/停用行為，確保現有執行個體保留其範本，而新的執行個體僅選取已啟用的範本。

由索引模型根據 Issue 內容生成。