Is it permissible for a man to declare his love to his fiancée who adheres to Islamic manners, and is it permissible for him to declare his love to his wife in front of people after marriage?

It is forbidden for a suitor to openly declare his love to his fiancée due to the potential for fitna (strife/temptation) that this may cause, as he is a stranger to her before the legal marriage contract. However, after marriage, it is permissible to express it, as long as it does not contradict custom and traditions.