To expand a bit more on anathemort's answer, AURAs themselves aren't really concerned with turn order at all. Rather, they add an effect to other targets and let Fantasy Ground's effect logic do the rest. Unfortunately, since neither FG itself, nor the linked Better Combat Effects extension has support for adding temporary hit points at the end of a character's turn, there isn't a clean way to automate this. However, if you are willing to make the concession of the temporary hit points being gained at the start of a character's turn, you could use the
Feature: TEMPO and ROLLON extension alongside this one.