[v1.1] UI: App Settings default to System theme

[patrickd-]

Expected task duration: 1 hour
Reward for accepted PR: US$25

Summary

The App's settings, which become visible by clicking on the gear icon in the top-right corner, currently always use a dark-mode theme. They should instead respect the System setting, and display the Settings in the same mode. ie. If the system's setting is dark mode, then use dark mode, but if not, don't.

Details

The culprit here is most likely the use of android:theme="@style/Theme.AppCompat"

It needs to be tested whether this line can be simply removed from the AndroidManifest.xml without breaking anything. Alternatively it should be tried if the application's own theme can be used, the one that the MainActivity uses. If it breaks without AppCompat then using Theme.AppCompat.DayNight should do the trick instead.