Fix preview for local collection links (#38793)

app/javascript/mastodon/features/collections/components/collection_preview_card.tsx

@@ -1,3 +1,5 @@
+import classNames from 'classnames';
+
 import type { CollectionLockupProps } from 'mastodon/features/collections/components/collection_lockup';
 import { CollectionLockup } from 'mastodon/features/collections/components/collection_lockup';
 
@@ -13,7 +15,7 @@ export const CollectionPreviewCard: React.FC<CollectionPreviewCardProps> = ({
   ...otherProps
 }) => {
   return (
-    <div className={classes.wrapper}>
+    <div className={classNames(classes.wrapper, 'collection-preview')}>
       <CollectionLockup collection={collection} {...otherProps} />
     </div>
   );