Allows users to discard a running timer without creating a time entry.
A trash icon in the timer widget reveals a confirmation step ('Discard / Keep')
to prevent accidental data loss. Backend exposes a new DELETE /api/timer
endpoint that simply deletes the ongoingTimer row.
Allows users to retroactively correct the start time of an ongoing timer
without stopping it. A pencil icon in the timer widget opens an inline
time input pre-filled with the current start time; confirming sends the
new time to the backend which validates it is in the past before persisting.
