Move relevant features from study version to main version

[tamslo]

Could be possible to cherry-pick; dependent on #660

• Double-check privacy screen
• Double-check global error handling
• Logging (refactor to merge general and Firebase logging; should set some flag? Should not add Sinai-specific config, might want to disable for now)
• Screenshot/-cast generation (with proper login methods)
• Re-login after inactivity
  • Double-check routing (should not be possible to route back from/to login)
  • Not sure, which authentication to use here (only works with oauth-resource-owner-password-flow; maybe disable in other cases or need Face ID / Fingerprint / PIN for other methods
• Move login after onboarding again
• Think about using old colors