Bug: Blog posts in admin panel are not ordered chronologically

## Summary

### Admin panel
The **[blog post listing in the admin panel](https://ckan.org/admin/snippets/blog/blogpostpage/)** is currently not ordered chronologically, making it difficult to manage and locate recent content.

### Blog
Additionally, **one very old article from 2022** is appearing on the blog among recent posts, creating confusion. See it here: https://ckan.org/blog/recap-open-knowledge-brasil/

## Expected behavior

- Blog posts in the admin panel should be **sorted by publish date (newest first)**
- Recently published articles should appear at the top
- Older content should not appear among recent posts

Start from the linked admin-panel blog post listing and the referenced 2022 blog article, then trace where their post ordering and publish dates are determined. Done means the admin list shows newest posts first and the old article no longer appears among recent blog posts.

Written by the indexing model from the issue text.