Look I made a mistake and attacked a planet that belonged to a legion that we have a pact with. Currently we have an alert system to warn us if we are about to attack someone we have a pact with can we do the same system with there planets also to avoid this problem
And with the changes to pacts I don't keep track all the time.

If your legions have an official, diplomacy tab NAP, you already DO get a warning when you click attack. "Soft" NAPs are unofficial, gentlemen's agreements and the game is not responsible for those. Trade Pacts and Battle Pacts have no bearing on Non Aggression Pacts so they do not nor should they give you a warning.