Allow fully offline-first 🔌

It's tedious to allow Play Store review validation forcing a Google account selection which must be allowed in GCP tester as well.

Given that the app should work offline, it should also work without any Google Tasks data available.

[x] Add a "Skip" button in onboarding
- using Scaffold to use TopAppBar & action with Text("Skip")
- OR putting the skip button at bottom end (to keep room for error message below "Authorize" button)
[x] Handle "not signed-in" in main app workflow to prevent the onboarding screen when explicitly skipped
- a quick & dirty solution would be to use an empty token and reason about that…
[x] Allow sign-in when clicking on "unsigned" profile icon
- with a dropdown menu that could be reused to sign-out and reaching settings
[x] In this setup, we would land in empty state, add a way to create first list
- either add a "Create task list" in empty state only with dedicated alert to enter name
- OR always add a "create task list" button "somewhere"

opatry / taskfolio