cover: Change the logic again:

- Work on feeds.
- Add `.is-cover` to modify the behaviours of columns.
- Only apply logic for dimensions on the cover container; too many contextual side effects otherwise.
- Add classes to dimension and align, including auto margins for flex.
- Rename classes in templates accordingly.

bookwyrm/templates/lists/list_items.html

@@ -13,8 +13,8 @@
                 {% if list_books %}
                     <div class="card-image columns is-mobile is-gapless is-clipped">
                         {% for book in list_books %}
-                            <a class="column is-narrow" href="{{ book.book.local_path }}">
-                                {% include 'snippets/book_cover.html' with book=book.book cover_class='is-min-w-none is-h-small' aria='show' %}
+                            <a class="column is-cover" href="{{ book.book.local_path }}">
+                                {% include 'snippets/book_cover.html' with book=book.book cover_class='is-h-s' aria='show' %}
                             </a>
                         {% endfor %}
                     </div>