Is one who completed the calculations for designing an air conditioning system for a bar, after a fatwa was issued prohibiting it, considered among those who are cursed? And is he obligated to offer expiation or donate the value of the days he worked?

It is forbidden to work on designing an air conditioning system for a place designated for drinking alcohol, because it involves an affirmation of evil and assistance in sin. The wages earned from this work must be disposed of by spending them on charitable causes, for anything that is forbidden, earning compensation for it is also forbidden. As for being among those cursed for assisting in drinking alcohol, this does not apply if one was ignorant of the prohibition or if one made sincere repentance; for whoever repents, Allah accepts his repentance. The questioner must repent for completing the work after becoming aware of its prohibition.