left_sidebar: Fix Enter key behavior on "Show all topics" link.

This commits adds href attribute so that pressing down
Enter key works on the anchor element and also makes the focus styling same topic names.

web/styles/left_sidebar.css

@@ -425,7 +425,8 @@
 #direct-messages-list .bottom_left_row {
     a.stream-name:focus,
     a.sidebar-topic-name:focus,
-    a.conversation-partners:focus {
+    a.conversation-partners:focus,
+    a.sidebar-topic-action-heading:focus {
         outline: none;
         text-decoration: none;
     }
@@ -522,6 +523,12 @@ ul.filters {
         }
     }
 
+    .sidebar-topic-action-heading {
+        &:focus {
+            color: var(--color-text-sidebar-action-heading);
+        }
+    }
+
     & hr {
         margin-top: 10px;
         margin-bottom: 10px;
@@ -1499,6 +1506,15 @@ li.top_left_scheduled_messages {
     width: 18px;
 }
 
+#stream_filters
+    .narrow-filter
+    .topic-list
+    .bottom_left_row:has(a.sidebar-topic-action-heading:focus-visible) {
+    outline: 2px solid var(--color-outline-focus);
+    outline-offset: -2px;
+    background-color: var(--color-background-hover-narrow-filter);
+}
+
 /* The grouping border should not be shown
    on zoomed-in views. */
 .zoom-in .topic-list.topic-list-has-topics::before,

web/templates/more_topics.hbs

@@ -2,7 +2,7 @@
   {{#unless more_topics_unreads}}zero-topic-unreads{{/unless}}
   {{#if more_topics_unread_count_muted}}more_topic_unreads_muted_only{{/if}}">
     <div class="topic-box">
-        <a class="sidebar-topic-action-heading" tabindex="0">{{t "Show all topics" }}</a>
+        <a href="" class="sidebar-topic-action-heading" tabindex="0">{{t "Show all topics" }}</a>
         <div class="topic-markers-and-unreads">
             {{#if more_topics_have_unread_mention_messages}}
                 <span class="unread_mention_info">