Basic sandbox refinement

The basic layout is here but need some refinements for later:

[x] Category limit in settings does not match anymore the category list layout which is now on 4 category by row, so it must be multiple of 4, i recommend a limit to 8 at least or 12 at maximum;
[x] Migration to Bootstrap 5.1.x ?
[x] Category detail content is not really styled, it's a little bit rude. It need basic styling;
[x] Article states should be reflected with icon(accumulated? or keeping the most important one when there is multiple states?) (using Bootstrap icons);
[x] Category and Article images are very basic blue squares, this never match any of available space. Article cover should be a little taller, Category cover may keep its square size, Article large image need something more large like an image for a Hero component. Finally, either each image have a different color (but will be a little ugly) or we create something more like common placeholder (grey image with its size written in or a text like "Article cover", etc..);
[x] There is no breadcrumb #23;

emencia / django-blog-lotus