fix: anchor floor on re-enable; breaker on scheduled panic; propagate next-run err; reject negative interval; close phantom runs on startup

internal/httpapi/tasks.go

@@ -53,7 +53,12 @@ func (s *Server) handleGetTask(w http.ResponseWriter, r *http.Request) {
 	for _, a := range accs {
 		views = append(views, accountDTO(a))
 	}
-	writeJSON(w, http.StatusOK, map[string]any{"task": s.taskViewFor(r.Context(), task), "accounts": views})
+	tv, err := s.taskViewFor(r.Context(), task)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"task": tv, "accounts": views})
 }
 
 // taskView augments the stored task with the server-computed next scheduled run
@@ -63,15 +68,17 @@ type taskView struct {
 	NextRunAt *string `json:"next_run_at"`
 }
 
-func (s *Server) taskViewFor(ctx context.Context, t store.Task) taskView {
-	var nextRunAt *string
-	if t.ScheduleIntervalSeconds > 0 && !t.Broken && t.Status != "running" && t.ScheduleAnchor != nil {
-		last, _ := s.store.LastFinishedRunAt(ctx, t.ID)
-		n := scheduler.NextRun(time.Duration(t.ScheduleIntervalSeconds)*time.Second, *t.ScheduleAnchor, last)
-		str := n.UTC().Format(time.RFC3339)
-		nextRunAt = &str
+func (s *Server) taskViewFor(ctx context.Context, t store.Task) (taskView, error) {
+	if t.ScheduleIntervalSeconds <= 0 || t.Broken || t.Status == "running" || t.ScheduleAnchor == nil {
+		return taskView{Task: t}, nil
 	}
-	return taskView{Task: t, NextRunAt: nextRunAt}
+	last, err := s.store.LastFinishedRunAt(ctx, t.ID)
+	if err != nil {
+		return taskView{}, err
+	}
+	n := scheduler.NextRun(time.Duration(t.ScheduleIntervalSeconds)*time.Second, *t.ScheduleAnchor, last)
+	str := n.UTC().Format(time.RFC3339)
+	return taskView{Task: t, NextRunAt: &str}, nil
 }
 
 // handleSetSchedule enables/changes/disables a task's recurring schedule.
@@ -89,6 +96,10 @@ func (s *Server) handleSetSchedule(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "bad json", http.StatusBadRequest)
 		return
 	}
+	if body.IntervalSeconds < 0 {
+		http.Error(w, "interval_seconds must be >= 0", http.StatusBadRequest)
+		return
+	}
 	if body.IntervalSeconds > 0 {
 		accs, err := s.store.ListAccountsByTask(r.Context(), taskID)
 		if err != nil {