Enhance history management with export and import functionalities

- Added endpoints for exporting generations as ZIP archives and audio files.
- Implemented import functionality for generations from ZIP archives with validation.
- Updated HistoryTable component to support new export and import features.
- Improved error handling and user notifications for export/import processes.
- Refactored related hooks and API client methods to accommodate new functionalities.

app/src/components/VoiceProfiles/ProfileList.tsx

@@ -58,11 +58,7 @@ export function ProfileList() {
   };
 
   if (isLoading) {
-    return (
-      <div className="flex items-center justify-center p-8">
-        <div className="text-muted-foreground">Loading profiles...</div>
-      </div>
-    );
+    return null;
   }
 
   if (error) {