Is rejoicing at the prospect of marriage and expressing that to friends considered a lie or an transgression?

What you mentioned is not a lie, for lying is informing about something that has passed contrary to its reality. What you did is to have a good opinion of Allah and optimism about your marriage being near. What is Islamically required is to have a good opinion of Allah, and the Prophet, peace and blessings be upon him, used to like good omens because they involve having a good opinion of Allah.