Deleted articles are now safely backed up before removal

Deleting an article used to be a one-way operation. If you deleted the wrong one, the only recovery path was a manual database restore from backups.

This release introduces a soft-delete-with-backup system:

• Every deleted article is automatically copied into a dedicated deleted_articles audit table before removal.
• The backup preserves the full article state plus metadata: who deleted it, when, and which project and author it belonged to.
• A database trigger handles the backup automatically — there's no application code path that can skip it.
• Optimized indexes keep queries against the deleted-articles archive efficient even at scale.

From your perspective, deletion behaves the same. But if you ever need us to recover an accidentally-deleted post, we now have a clean, auditable path to bring it back.