UX: Topic cards v2 (#173)

This is the second iteration on the topic card design, in which we bring
back the OP and change the layout.

**Changes**:
* Show OP avatar
* Remove activity avatar and replace by reply icon
* Remove activity icon background
* Move category tag to top left
* Replace long activity copy ("…replied at…") with dot separator
* Change date formatting to `tiny`
* Adjust bulk select styling to new layout + align checkbox to top on
mobile VS keep centred on desktop

* Why: On desktop, the avatar is taking 2 lines (usually) and aligning
the checkbox vertically looks nice. Exception for excerpts, but since
that's only available for pinned topics atm that's a low occurrence. On
mobile, the topic card is 3 lines, with a smaller avatar, which makes
the checkbox "float" around a bit when centred. Hence aligning it to the
top, which for solid avatars aligns nicely too.

* CSS refactor: grid, breakpoints

Messages/bookmarks have not been changed.

| Description | Visual |
|--------|--------|
| Large topic list | ![CleanShot 2025-06-02 at 17 37
35@2x](https://github.com/user-attachments/assets/f232058e-dbf6-4689-abe3-65970464a3e3)|
| Large bulk edit | ![CleanShot 2025-06-02 at 17 37
17@2x](https://github.com/user-attachments/assets/03d86b5f-d62b-4449-9c0b-452ceb8be60c)
|
| Medium topic list | ![CleanShot 2025-06-02 at 17 39
01@2x](https://github.com/user-attachments/assets/80739641-cf8f-4095-938f-9781cac57a7d)
|
| Medium bulk edit | ![CleanShot 2025-06-02 at 17 39
24@2x](https://github.com/user-attachments/assets/6e9045af-734a-4f3f-830a-e03a2f06fdd8)
|
| Small topic list | ![CleanShot 2025-06-02 at 17 39
44@2x](https://github.com/user-attachments/assets/eeca80bc-6863-4026-8f19-b1b5cf6848f3)
|
| Small bulk edit | ![CleanShot 2025-06-02 at 17 40
00@2x](https://github.com/user-attachments/assets/cde7be08-cde2-4ff2-b81b-328d3d7be848)
|
| Messages page (remains unchanged) | ![CleanShot 2025-06-02 at 17 20
37@2x](https://github.com/user-attachments/assets/6512bfe9-a699-4c67-b709-166540ee6fde)
|
| Bookmark page (remains unchanged) | ![CleanShot 2025-06-02 at 17 21
01@2x](https://github.com/user-attachments/assets/f8f43638-e911-49cb-a0d5-ebcb51ccfba4)
|

javascripts/discourse/initializers/topic-list-columns.gjs

@@ -1,6 +1,7 @@
 import { withPluginApi } from "discourse/lib/plugin-api";
 import TopicActivityColumn from "../components/card/topic-activity-column";
 import TopicCategoryColumn from "../components/card/topic-category-column";
+import TopicCreatorColumn from "../components/card/topic-creator-column";
 import TopicLikesColumn from "../components/card/topic-likes-column";
 import TopicRepliesColumn from "../components/card/topic-replies-column";
 import TopicStatusColumn from "../components/card/topic-status-column";
@@ -30,6 +31,12 @@ const TopicLikesReplies = <template>
   </td>
 </template>;
 
+const TopicCreator = <template>
+  <td class="topic-creator-data">
+    <TopicCreatorColumn @topic={{@topic}} />
+  </td>
+</template>;
+
 export default {
   name: "topic-list-customizations",
 
@@ -52,6 +59,10 @@ export default {
             item: TopicLikesReplies,
             after: "topic-author-avatar",
           });
+          columns.add("topic-creator", {
+            item: TopicCreator,
+            after: "topic-author-avatar",
+          });
           columns.delete("views");
           columns.delete("replies");
           if (!router.currentRouteName.includes("userPrivateMessages")) {