- Implement `GET /api/backup` to stream `data` directory as a tarball using `node-tar`.
- Implement `POST /api/restore` to accept and extract tarballs to the `data` directory.
- Update `BackupRestoreDialog` to accept `.tar` files and remove gzip references.
- Ensure safe restore with database connection management and rollback.
- Disabled Gzip compression as requested since assets are already compressed WebP files.