Is it permissible to go to the mosque for Fajr prayer without the father's knowledge, given his refusal due to fear for his son's safety?

Obedience to parents is obligatory, unless they command disobedience to Allah. There is no obedience to a creature in disobedience to the Creator. Congregational prayer is obligatory, and it is not permissible for a father to prevent his adult son from it; rather, he must command him to perform it. If the father commands his son to abandon congregational prayer, he has commanded disobedience, so there is no obedience to him then. Nevertheless, he must be treated with kindness and beneficence. The son can go out to pray secretly if the parent does not respond to persuasion, but this does not lift the sin from the parent. The parent must be a good role model for his family and command them to pray, and he should know that whoever prays Fajr is under the protection of Allah.