How to set dark/light app icon to be shown in /settings/apps?

Two-Factor Email has no menu entry, so I cannot use appinfo/info.xml’s “navigations” section to set an icon file name. I noticed that my app icon is recognized in “settings/apps” if I place/name it “img/app.svg”. There should be another way to explicitly set a custom name for the app icon shown to the user, or documentation that it has to be “app.svg”.

Even if my app had a menu and I would have set an icon file name, I could only set one. So this mechanism seems to lack support for dark/light theming. But since core apps seem to be able to set dark/light icons: How to do it (correctly, NC 25 theming)? Please advise/hint…I didn’t find how to do it.

Have you checked that the image is in fact a different one for light/dark mode? Maybe it looks only like this and is styled via CSS?

Honestly, I have not had a closer look but saw in the files app no obvious second image. So, I wonder if this app is not using one image for all cases…