css: refactor CSS to use Tailwind-style utility classes.

Refactor CSS to use standard Tailwind-style utility classes instead of
ad-hoc rules. This eliminates a lot of single-purpose rules for specific
UI elements and standardizes margins to be more consistent throughout
the site.

Utility classes are defined manually on an as-needed basis instead of
importing Tailwind as a whole. Naming conventions mostly follow
Tailwind's conventions, otherwise they follow Bootstrap.

* https://tailwindcss.com/docs/
* https://getbootstrap.com/docs/5.0/utilities/spacing/

app/components/tag_list_component/tag_list_component.html.scss

@@ -1,4 +1,8 @@
 .tag-list {
+  a.wiki-link {
+    margin-right: 0.25rem;
+  }
+
   a.search-tag {
     overflow-wrap: normal;
   }
@@ -11,9 +15,7 @@
     }
   }
 
-  &.categorized-tag-list {
-    ul {
-      margin-bottom: 1em;
-    }
+  ul {
+    margin-bottom: 1em;
   }
 }