add bookmark button to thread and posts in thread view

sass/_default.scss

@@ -213,6 +213,13 @@ $thread_title_size: 1.5rem !default;
   font-weight: bold;
 }
 
+$thread_actions_gap: $SMALL_PADDING !default;
+.thread-actions {
+  display: flex;
+  align-items: center;
+  gap: $thread_actions_gap;
+}
+
 $post_usercard_width: 200px !default;
 $post_border: 2px outset $DARK_2 !default;
 .post {
@@ -747,6 +754,10 @@ $thread_locked_background: none !default;
   align-items: center;
   justify-content: center;
   flex-direction: column;
+
+  &.inline {
+    display: inline-flex;
+  }
 }
 
 $post_img_container_gap: $SMALL_PADDING !default;