Show admin toggle, but disable for current user

You shouldn't be able to demote yourself but displaying the disabled
toggle helps explain the group of admins at the top of the list. Builds
upon #140

app/assets/stylesheets/buttons.css

@@ -127,6 +127,13 @@
     }
   }
 
+  &:has(input[type=checkbox][disabled]) {
+    cursor: not-allowed;
+    filter: grayscale(100%) contrast(0.5);
+    opacity: 0.5;
+    pointer-events: none;
+  }
+
   [disabled] &[type=submit],
   &[type=submit]:disabled {
     cursor: not-allowed;

app/views/accounts/users/_user.html.erb

@@ -9,13 +9,13 @@
 
   <hr class="separator" aria-hidden="true">
 
-  <% if Current.user.can_administer? && user != Current.user && user.active? %>
+  <% if Current.user.can_administer? && user.active? %>
     <% unless user.bot? %>
       <%= form_with model: user, url: account_user_path(user), data: { controller: "form" }, method: :patch do | form | %>
         <label class="btn txt-small flex-item-no-shrink" for="<%= dom_id(user, :role) %>">
           <span class="for-screen-reader">Role: <%= user.administrator? ? "Administrator" : "Member" %></span>
           <%= image_tag "crown.svg", size: 20, aria: { hidden: "true" } %>
-          <%= form.check_box :role, { data: { action: "form#submit" }, hidden: true, id: dom_id(user, :role) }, "administrator", "member" %>
+          <%= form.check_box :role, { data: { action: "form#submit" }, hidden: true, id: dom_id(user, :role), disabled: user == Current.user }, "administrator", "member" %>
         </label>
       <% end %>
     <% end %>