nk app 1: add download links for nitrokey app 1 (#570)

[blu-nitro]

closes #570

[github-actions]

The successful documentation build for e1a57bf was deployed for preview:

• https://docspreview.nitrokey.com/PR-585

generated by workflow run 29012552418 (attempt 1)

[jans23]

The section for Ubuntu is missing. Is this on purpose?

[jans23]

The first sentences are redundant.

The list should be sorted alphabetically.

Fix dead links:

• "cask" in macos
• "is part" in nixos
• "is part" in gentoo

[ABuljko]

In https://www.nitrokey.com/download/appimage-flatpak-snap

"AppImage, Flatpak, Snap" is the main title while each section behaves like a subtitle
But in the code each are like their own title. Should remake it like in the app? (the ubuntu section has a link to in the www.nitrokey so i would like that so it is still connected as before)

[ABuljko]

Gentoo

There's a working archive.org snapshot from November 12, 2024 (just before the package was removed):
https://web.archive.org/web/20241112195418/https://github.com/gentoo/gentoo/tree/master/app-crypt/nitrokey-app

Maybe we could use that as a reference link alongside the "package removed" note, so Gentoo users can still see the historical ebuild.

NixOs

https://github.com/NixOS/nixpkgs/tree/master/pkgs/by-name/ni/nitrokey-app

The package moved locations in nixpkgs but is still active. That link should be working.
Should I add it instead?

macOS

Could not find an alternative (should I remove it and look for an alternative)

[jans23]

"AppImage, Flatpak, Snap" should be individual sections (as you have it already).

Remove sections Gentoo and Homebrew as well as title "Single-file download".

Yes, update the link for NixOS.

[ABuljko]

In the https://www.nitrokey.com/download/ubuntu
The text link "here" leads to the section containing all three
I would have to change the text a bit since in the code they are registered as separate

[jans23]

No need for these clickable sections in Windows, macOS, FreeBSD, and Source.

[jans23]

Update the hyperlink in nk-app2.rst

[jans23]

@ABuljko you need to fix the CI tests.

[ABuljko]

@jans23 can I do the honors haha