Dark mode fixes

[the-dagger]

Fixes #502

[samtstern]

There's still something wrong here. For example look at the check email screen. The label and hint text color are white on my Pixel:

[the-dagger]

Hm, that's strange.
I'm using OnePlus 3 on Android 7.0 and it runs fine.
Hold on, I'll test it on an emulator as well

[samtstern]

@the-dagger did you ever figure this out, or should we close this PR for now?

[the-dagger]

Hey Sam, I tried running it on various emulators and it worked fine for me. I got a bit busy this week, so will give this a go again this weekend to figure out what the issue was.

[samtstern]

@the-dagger it's been over a month since either of us updated this PR so I am going to close it in the name of housekeeping. Please feel free to comment/re-open in the future if you ever come back to it!