Improve dashboard health and state recovery

internal/scheduler/scheduler.go

@@ -14,6 +14,21 @@ type Enqueue func(model.Job) error
 type EnqueueMaintenance func(string, string) (model.Run, error)
 type LastRun func(string) time.Time
 
+func PreviousScheduled(spec, timezone string, now time.Time, window time.Duration) (time.Time, error) {
+	expression, err := Parse(spec)
+	if err != nil {
+		return time.Time{}, err
+	}
+	loc := time.Local
+	if timezone != "" {
+		loc, err = time.LoadLocation(timezone)
+		if err != nil {
+			return time.Time{}, err
+		}
+	}
+	return previous(expression, now.In(loc), window).UTC(), nil
+}
+
 type Scheduler struct {
 	config      ConfigProvider
 	enqueue     Enqueue