Back button closes tags menu or add overlay

[SaschaCowley]

Is your feature request related to a problem? Please describe.
After tapping the add FAB or the tags button, I think it would be intuitive to press the system back button to go back to the cards view. However, if I do this, I'm taken out of the app.

Describe the solution you'd like
I believe that using the system back button after activating the tags or add menus should close these menus.

Describe alternatives you've considered
The user can already close these menus via the app.

Additional context
I think the existing method of closing these screens purely via the app is not in keeping with standard UI components. For example, if you open the app options menu, it can be closed by pressing the system back button or by tapping outside the menu. A similar mechanic would be intuitive for the tags and add menus.