Ente Auth export options don't use portals on Linux

[kolon0]

Description

While import options use portals on Linux, export options don’t. Instead, they directly export to the Downloads directory. The user can't choose where to save the file.

There is also Ente Auth's official Flatpak. Flatpaks are expected to use portals. If we can use portals for importing, we should be able to do the same for exporting.

While I don’t know Flutter, it looks like the issue comes from there: export_widget.dart#L156C7-L163C8.

We should use FilePicker’s saveFile method instead of PlatformUtil.shareFile. This will allow us to handle exporting properly.

Thank you for this amazing project!

Version

v4.3.2

What product are you using?

Ente Auth

What platform are you using?

Desktop - Linux