Fleet service records created from vendor bills now show the related bill, calculate the bill amount correctly, and protect billed costs from manual changes or deletion. This improves consistency between fleet expenses and accounting records, with clearer bill status shown through the smart button color.

With this commit, the bill's amount is correctly computed. If the service log is generated by a bill, the cost is readonly to be consistent.
If the service log is generated by a bill, it can't be deleted.

The bill smartbutton's color is related to the bill's state.

task-3783017