Is it permissible to receive a financial bonus this year for conducting a financial inventory of previous years, given that the bonus was not disbursed at the time the work was performed?

As long as you have agreed with the responsible parties on a financial reward for the inventory process and you have carried it out, then you have the right to take it or waive it. It is a debt owed to you by the institution unless you waive it. If it is paid to you, there is no harm in taking it. As for your refusal to work with them again on inventory, there is nothing wrong with that, unless the employment contract or custom obliges you to do so.