perf: virtualize remaining long result views

Reduce DOM growth across resource, history, workflow, share, downloading, and message views so large datasets stay responsive while scrolling.

src/utils/torrentDownloadCache.ts

@@ -0,0 +1,13 @@
+import { reactive } from 'vue'
+
+const downloadedTorrentMap = reactive<Record<string, boolean>>({})
+
+export function markTorrentDownloaded(url?: string | null) {
+  if (!url) {
+    return
+  }
+
+  downloadedTorrentMap[url] = true
+}
+
+export { downloadedTorrentMap }