A repeated submit that wrote nothing reads as a neutral notice rather
than a success. The delete control is entered in the destructive-control
registry, and its 409 code in the published error catalogue.
Refs #1085
A small sheet with sport, start, duration and optionally distance and
active energy, nothing else. The start is read in the profile timezone,
distance in the reader's unit and stored in metres. It saves through
POST /api/workouts/batch as source MANUAL with an external id minted once
per opened form, so a second tap lands as a duplicate, not a second row.
The workouts page carries the action in its header and in the empty
state; the detail page offers delete for a hand-entered workout.
Refs #1085
Marc-André Bombeck