When the Oban queue backs up, the 60-second uniqueness window expires
and duplicate jobs stack up per device. Switch to period: :infinity so
only one poll/monitor job exists per device at any time. Add replace
option to supersede stale scheduled jobs with updated scheduled_at.
Remove :executing from unique states so self-scheduling works while
the current job runs. Set max_attempts: 1 since retrying stale polls
is pointless.
Also fix all credo --strict issues across the codebase.
