ZipStream writes via fwrite(php://output) which FrankenPHP silently
drops, resulting in 0-byte ZIP downloads. Switch to ZipArchive to build
the ZIP as a temp file on disk, then serve with response()->download().
- Rewrite download() to use ZipArchive + BinaryFileResponse
- Remove decryptFileToCallback() from FileEncryptionService
- Update tests for BinaryFileResponse instead of StreamedResponse
- Remove maennchen/zipstream-php dependency
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
