Update modified timestamp when updating motion

internal/models/motions.go

@@ -820,8 +820,8 @@ func (m *MotionModel) GetByID(ctx context.Context, id int64) (*Motion, error) {
 func (m *MotionModel) Update(ctx context.Context, id int64, voteType *VoteType, title string, content string, due time.Time) error {
 	_, err := m.DB.ExecContext(
 		ctx,
-		`UPDATE decisions SET title=?, content=?, votetype=?, due=? WHERE id=?`,
-		title, content, voteType, due.UTC(), id,
+		`UPDATE decisions SET title=?, content=?, votetype=?, due=?, modified=? WHERE id=?`,
+		title, content, voteType, due.UTC(), time.Now().UTC(), id,
 	)
 	if err != nil {
 		return fmt.Errorf("could not update decision: %w", err)