fix(downloads): harden enqueue lifecycle races

Reject superseded enqueue generations in the queue manager and coordinate frontend dispatch, pause, removal, and property mutations.

src/components/DownloadTable.tsx

@@ -338,7 +338,7 @@ export const DownloadTable: React.FC<DownloadTableProps> = ({ filter }) => {
     }
 
     try {
-      await invoke('pause_download', { id });
+      await useDownloadStore.getState().pauseDownload(id);
     } catch (e) {
       console.error("Failed to pause:", e);
       showInteractionError('Could not pause download', e);