[Request]: Exclude application data from backups via `isExcludedFromBackupKey`

### Feature or enhancement request details

The application data at `~/Library/Application Support/com.apple.container/` holds large sparse files whose size exceeds actual allocation, causing backup tools to fail. Consider setting `URLResourceKey.isExcludedFromBackupKey = true` on the application data folder to resolve this.

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

Locate the code that creates or manages ~/Library/Application Support/com.apple.container/ and read how the application data folder is initialized. Verify the folder receives URLResourceKey.isExcludedFromBackupKey and confirm that the resulting backup metadata prevents backup tools from processing its sparse files.

Written by the indexing model from the issue text.