Remove the TODO about mocking the repo in controller tests

Not worth it; the backend mock works fine.
Remove residues of --quiet. Consolidate names of envoronment variables.
Move view out of the model directory

It really is infrastructure and doesn't belong to the domain.
Add scheduler
Mock the scheduler for all tests involving pomodori.

Prevents us from getting a lot of at jobs in the at queue (no need to mock Open3.capture3 for pomodoro tests).
Move exec to its own module for reuse in Scheduler and Job
Add Scheduler#clear
Remove the last un-stubbed call to the Scheduler from tests
Simplify scheduler test by using the real at with a dedicated test queue 't'
Clear the at queue on start