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/views/posts/index.html.erb

@@ -16,7 +16,7 @@
 <% end %>
 
 <% content_for(:content) do %>
-  <menu id="post-sections">
+  <menu id="post-sections" class="mb-4">
     <li class="active"><a href="#" id="show-posts-link">Posts</a></li>
 
     <% if @post_set.artist.present? %>

app/views/posts/partials/common/_search.html.erb

@@ -2,11 +2,11 @@
 
 <section id="search-box">
   <h2>Search</h2>
-  <%= form_tag(path, method: "get", id: "search-box-form") do %>
+  <%= form_tag(path, method: "get", id: "search-box-form", class: "flex") do %>
     <% if params[:random] %>
       <%= hidden_field_tag :random, params[:random] %>
     <% end %>
-    <%= text_field_tag("tags", tags, :id => tags_dom_id, :"data-shortcut" => "q", :"data-autocomplete" => "tag-query") %>
+    <%= text_field_tag("tags", tags, :id => tags_dom_id, :class => "flex-auto", :"data-shortcut" => "q", :"data-autocomplete" => "tag-query") %>
     <button id="search-box-submit" type="submit"><%= search_icon %></button>
   <% end %>
 </section>

app/views/posts/partials/index/_excerpt.html.erb

@@ -15,7 +15,7 @@
         <%= render "artists/summary", artist: artist %>
         <%= render "tag_relationships/alias_and_implication_list", tag: artist.tag %>
 
-        <p class="links">
+        <p class="mt-4">
           <% if artist.wiki_page.present? %>
             <%= link_to "View wiki", artist.wiki_page, id: "view-wiki-link" %> |
           <% end %>
@@ -33,7 +33,7 @@
         <%= format_text(wiki_page.body) %>
         <%= render "tag_relationships/alias_and_implication_list", tag: wiki_page.tag %>
 
-        <p class="links">
+        <p class="mt-4">
           <%= link_to_wiki "View wiki", wiki_page.title, id: "view-wiki-link" %>
         </p>
       </div>
@@ -52,7 +52,7 @@
         <%= format_text(post_set.pool.description) %>
       </div>
 
-      <p class="links">
+      <p class="mt-4">
         <%= link_to "View pool", pool_path(post_set.pool.id) %>
       </p>
     <% end %>

app/views/posts/partials/show/_information.html.erb

@@ -28,7 +28,7 @@
     <% if policy(post).can_view_favlist? %>
     <%= link_to "Show »", "#", id: "show-favlist-link", style: ("display: none;" if post.fav_count == 0) %>
     <%= link_to "« Hide", "#", id: "hide-favlist-link", style: "display: none;" %>
-    <div id="favlist" style="display: none;">
+    <div id="favlist" style="display: none;" class="ml-4">
       <%= render "posts/partials/show/favorite_list", post: post %>
     </div>
   <% end %></li>

app/views/posts/partials/show/_ugoira_original.html.erb

@@ -10,16 +10,14 @@
 ) %>
 
 <div id="ugoira-controls">
-  <div id="ugoira-control-panel" style="width: <%= [@post.image_width, 350].max %>px;">
+  <div id="ugoira-control-panel" class="mb-2 flex items-center" style="width: <%= [@post.image_width, 350].max %>px;">
     <%= button_tag "Play", :id => "ugoira-play", :style => "display: none;" %>
     <%= button_tag "Pause", :id => "ugoira-pause" %>
-    <div id="seek-slider" style="width: <%= [@post.image_width, 350].max - 81 %>px;"></div>
+    <div id="seek-slider" class="ml-4" style="width: <%= [@post.image_width, 350].max - 81 %>px;"></div>
   </div>
-  <p id="save-video-link">
-    <% if post.has_ugoira_webm? %>
-      <%= link_to "Save as video (right click and save)", post.tagged_large_file_url %>
-    <% else %>
-      WebM conversion pending
-    <% end %>
-  </p>
+  <% if post.has_ugoira_webm? %>
+    <%= link_to "Save as video (right click and save)", post.tagged_large_file_url %>
+  <% else %>
+    WebM conversion pending
+  <% end %>
 </div>

app/views/posts/show.html.erb

@@ -50,7 +50,7 @@
   <% end -%>
 
   <% if policy(Favorite).create? %>
-    <%= content_tag(:div, class: "fav-buttons fav-buttons-#{@post.favorited_by?(CurrentUser.user)}") do %>
+    <%= content_tag(:div, class: "mb-2 fav-buttons fav-buttons-#{@post.favorited_by?(CurrentUser.user)}") do %>
       <%= form_tag(favorites_path(post_id: @post.id), method: "post", id: "add-fav-button", "data-remote": true) do %>
         <%= button_tag empty_heart_icon, class: "ui-button ui-widget ui-corner-all", "data-disable-with": spinner_icon %>
       <% end %>
@@ -86,7 +86,7 @@
     <%= render_post_navbar(@post, current_user: CurrentUser.user, search: params[:q]) %>
   <% end %>
 
-  <menu id="post-sections">
+  <menu id="post-sections" class="mb-4">
     <li class="active"><a href="#comments">Comments</a></li>
 
     <% if RecommenderService.available_for_post?(@post) %>