[Android] Stay logged in or fingerprint login

Given I have a nice long passphrase on my keybase account, I shouldn't have to log in over and again whenever I get a new message.

I get a notification that there's a new encrypted chat message, click it and every time, my session has timed out. I then have to type a long password. Not a good experience.

My phone is encrypted and also uses a long password which I skip by using the fingerprint reader, my banks all allow login by fingerprint as well, keybase should allow this.

No files, tests, or entry points are named. Start by locating the Android session timeout and authentication flow, then define the supported fingerprint-login behavior and verify that opening an encrypted chat notification no longer requires repeatedly entering the long passphrase.

Written by the indexing model from the issue text.