Implement a per-application setting (`docker_images_to_keep`) in `application_settings` table to control how many Docker images are preserved during cleanup. The cleanup process now:
- Respects per-application retention settings (default: 2 images)
- Preserves the N most recent images per application for easy rollback
- Always deletes PR images and keeps the currently running image
- Dynamically excludes application images from general Docker image prune
- Cleans up non-Coolify unused images to prevent disk bloat
Fixes issues where cleanup would delete all images needed for rollback.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
4ed7a4238a