Allow separate lump-sum fees to be added and displayed at the end of the estimate

Several users have requested the ability to add lump-sum fees (such as overhead, administrative costs, profits, or specific fees) directly at the end of the quote, as a separate line item, rather than being required to break them down and include them in the unit price of each task. Users also want the option to choose which fees to hide (i.e., include them in the task prices, as with platform fees like those on Réno-Assistance) and which fees to display clearly at the bottom of the quote before the final total.