feat(ui): implement keyword highlighting and improve search experience

- Add keyword highlighting in `PostCard` and `PostContentRenderer` using `HighlightText`.
- Implement smart excerpt logic in `PostCard` to show relevant context around search keywords.
- Update `SearchBar` styles for better visual feedback and consistency.
- Enhance `SearchScreen` with modern tab variants and improved tag styling.
- Add support for updating group descriptions in `GroupInfoScreen` and `GroupService`.
- Refactor various UI components for improved layout stability and typography.

src/services/message/groupService.ts

@@ -301,6 +301,20 @@ class GroupService {
     return normalizeGroup(response.data);
   }
 
+  /**
+   * 设置群描述
+   * PUT /api/v1/groups/:id/description
+   */
+  async setGroupDescription(groupId: string, description: string): Promise<GroupResponse> {
+    const response = await api.put<GroupResponse>(
+      `/groups/${encodeURIComponent(groupId)}/description`,
+      {
+        description,
+      }
+    );
+    return normalizeGroup(response.data);
+  }
+
   // ==================== 群公告 ====================
 
   /**