My group members are trying to take credit for the group project that only I worked on. How do I stop this?
If you aren't interested in the job being offered, I'd just let this go. As far as the course project/grade is concerned, that issue is past. The project was a group project and was submitted as such. I assume the professor allowed you to organize the group as you saw fit, which resulted in your doing all of the work. I think that is poor practice for the professor. But the ship has sailed. You also had other options at the time for project organization or complaint that you didn't use. Yes, I see that you recognize that. 

But if you don't want/need the job you have little to gain by keeping your "friends" from taking it. 

If you do want it, however, you should visit the prof during office hours (no email for this sort of thing) and explain that the work was yours. He/she can probably verify this easily by asking you a few questions about it without the need for screen shots etc. I doubt that you would suffer by sticking to the truth, though your friends may resent it and you will need to explain why you treated it as a personal project rather than a group project. Yes, I understand the drivers that cause that, of course, which is why I don't care for the professor's willingness to let it happen. 

But also consider the fact that if he hires you and one of your friends you will be back in the same situation again, working with an unproductive partner. That might not be a good outcome for you in any case. 



Note: If a professor wants a "group" to create something he/she needs to also teach how to go about that. Letting inexperienced groups self-organize seldom results in a good outcome.