fix(ui): virtualize the Lens setup preview table

The preview wrapper scrolled instead of the table's own scroller, so the
virtualizer saw every row as visible and kept fetching pages. Each page
re-rendered thousands of rows and blocked typing for up to a second.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ui/litellm-dashboard/src/components/lens/setup/MatchingActivityPreview.tsx

@@ -114,7 +114,7 @@ export function MatchingActivityPreview({
         </div>
       )}
       {(status.loading || (shown && !status.error && runs.length > 0)) && (
-        <div className="max-h-[calc(100dvh-16rem)] min-h-0 overflow-auto">
+        <div className="flex max-h-[calc(100dvh-16rem)] min-h-0 flex-col">
           <PreviewTable
             traces={runs}
             isLoading={status.loading}