Add hide-on-mobile utility class

internal/assets/static/main.css

@@ -995,7 +995,7 @@ body {
         flex-flow: row-reverse;
     }
 
-    svg.forum-post-list-thumbnail {
+    .hide-on-mobile {
         display: none
     }
 }

internal/assets/templates/forum-posts.html

@@ -9,11 +9,11 @@
                 {{ if ne $post.ThumbnailUrl "" }}
                 <img class="forum-post-list-thumbnail thumbnail" src="{{ $post.ThumbnailUrl }}" alt="" loading="lazy">
                 {{ else if $post.HasTargetUrl }}
-                <svg class="forum-post-list-thumbnail" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="-9 -8 40 40" stroke-width="1.5" stroke="var(--color-text-subdue)">
+                <svg class="forum-post-list-thumbnail hide-on-mobile" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="-9 -8 40 40" stroke-width="1.5" stroke="var(--color-text-subdue)">
                     <path stroke-linecap="round" stroke-linejoin="round" d="M13.19 8.688a4.5 4.5 0 0 1 1.242 7.244l-4.5 4.5a4.5 4.5 0 0 1-6.364-6.364l1.757-1.757m13.35-.622 1.757-1.757a4.5 4.5 0 0 0-6.364-6.364l-4.5 4.5a4.5 4.5 0 0 0 1.242 7.244" />
                 </svg>
                 {{ else }}
-                <svg class="forum-post-list-thumbnail" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="-9 -8 40 40" stroke-width="1.5" stroke="var(--color-text-subdue)">
+                <svg class="forum-post-list-thumbnail hide-on-mobile" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="-9 -8 40 40" stroke-width="1.5" stroke="var(--color-text-subdue)">
                     <path stroke-linecap="round" stroke-linejoin="round" d="M7.5 8.25h9m-9 3H12m-9.75 1.51c0 1.6 1.123 2.994 2.707 3.227 1.129.166 2.27.293 3.423.379.35.026.67.21.865.501L12 21l2.755-4.133a1.14 1.14 0 0 1 .865-.501 48.172 48.172 0 0 0 3.423-.379c1.584-.233 2.707-1.626 2.707-3.228V6.741c0-1.602-1.123-2.995-2.707-3.228A48.394 48.394 0 0 0 12 3c-2.392 0-4.744.175-7.043.513C3.373 3.746 2.25 5.14 2.25 6.741v6.018Z" />
                 </svg>
                 {{ end }}