- Add `js/s3-quick.js` with `uploadWithManifest` and `uploadWithKeys`.
- Update `components/upload-modal.html` to add "Use presigned manifest" toggle and warning.
- Update `js/ui/components/UploadModal.js` to wire up the manifest upload flow.
- Add local persistence for quick S3 settings (though mainly handled by existing storage settings).
- Ensure keys are only used for client-side uploads or replaced by manifest flow.