deadline_at is a wall-clock timestamp, so pause time counted against the
task timeout: pausing overnight (or shutting the machine down while
paused) made the deadline ring while parked, and resuming landed
straight into the settle sequence and a timeout terminal state.
ApplyTaskPause now stamps paused_at, and ApplyTaskAdmission credits the
paused interval back onto deadline_at in the same atomic UPDATE that
ends the pause (paused_at is cleared there too). The shifted deadline
flows to the live handle via the existing RETURNING mirror, so the
engine clock context picks it up. Matches the re-basing the
archive-restore path already did for paused tasks.
Migration is an idempotent ADD COLUMN; tasks paused before the upgrade
have no paused_at and keep the old behavior.
Fixes#1
