DEV: Merge topic list card component (#17)

This PR merges the topic-list-item card component into the nextgen theme.

Also does the following cleanup:

* Use template-only ember components
* Use `fire` instead of deprecated `fa-fire` icon
* Lower version requirement for node to 18 to match core
* Add english locale strings for topic status column
* Remove dummy theme settings

---------

Co-authored-by: Martin Brennan <martin@discourse.org>

javascripts/discourse/components/card/topic-author-avatar-column.gjs

@@ -0,0 +1,9 @@
+import avatar from "discourse/helpers/avatar";
+
+const TopicAuthorAvatarColumn = <template>
+  <span class="topic-author-avatar">
+    {{avatar @topic.creator imageSize="large"}}
+  </span>
+</template>;
+
+export default TopicAuthorAvatarColumn;