Superset Desktop 0.0.64 Beta

Beta Windows installer for Superset Desktop 0.0.64.\n\nChanges:\n- Fix Windows installer asset layout to prevent startup failures.\n- Ensure desktop shortcut uses Superset icon.\n- Keep migrations outside asar to avoid package.json corruption.\n\nAssets:\n- Superset-0.0.64-x64.exe\n- Superset-0.0.64-x64.exe.blockmap\n- latest.yml