A task holds the whole night, not one end of it

One command per task was the wrong unit. A charging window is two commands
and reads as one intention, so it was two rows that had to be named twice,
switched off twice, and kept in step by hand — and there was nowhere to put
the third thing, the ease down to 10 A once the house is asleep.

So a task holds a flow. Steps are rows in the editor: an action, a time, and
the ceiling under the one action that takes one. The chargers and the days
belong to the task, because they are the same for every step of a night, and
the switch governs all of it.

The steps keep the order they were written rather than being sorted by the
clock. A night crosses midnight, and clock order files "start at 23:00" last,
behind the stop that closes it — which is not the flow anybody described.
Nothing about firing depends on the order: every step is timed on its own,
and the sweep asks each one whether its minute has come.

Run now moved onto the step. A flow is not a thing that can happen at once —
firing a start and the stop that closes it back to back would leave the
charger where it began and prove nothing — so the button fires the one line
it sits on, and the outcome names the step by its time.

The stored shape changes with it: action/amps/time give way to a steps list.
The collection was a day old and empty, so this replaces them outright rather
than carrying a compatibility path for a schema nothing has run on.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

API Server/internal/api/server.go

@@ -502,7 +502,7 @@ func (s *Server) Handler() http.Handler {
 	mux.HandleFunc("POST /api/charging-tasks", s.createChargingTask)
 	mux.HandleFunc("PATCH /api/charging-tasks/{id}", s.updateChargingTask)
 	mux.HandleFunc("DELETE /api/charging-tasks/{id}", s.deleteChargingTask)
-	mux.HandleFunc("POST /api/charging-tasks/{id}/run", s.runChargingTaskNow)
+	mux.HandleFunc("POST /api/charging-tasks/{id}/steps/{step}/run", s.runChargingStepNow)
 
 	// Cars + sharing.
 	mux.HandleFunc("GET /api/cars", s.listCars)