Add subtask model and repository, implement webhook notification handling

fix Issue with Scheduler
Support NotificationPlatformWebhook
support Discord as notification target

internal/chore/scheduler.go

@@ -38,9 +38,8 @@ func scheduleNextDueDate(chore *chModel.Chore, completedDate time.Time) (*time.T
 		if err != nil {
 			return nil, fmt.Errorf("error parsing time in frequency metadata: %w", err)
 		}
-
+		t = t.UTC()
 		baseDate = time.Date(baseDate.Year(), baseDate.Month(), baseDate.Day(), t.Hour(), t.Minute(), t.Second(), 0, time.UTC)
-
 		// If the time is in the past today, move it to tomorrow
 		if baseDate.Before(completedDate) {
 			baseDate = baseDate.AddDate(0, 0, 1)