I’m wondering if there’s a way to create a slideshow in after effects with forward and reverse buttons. In other words, once you export the composition as a .mov, you can control the playing of the slideshow with buttons that allow you to navigate forward or backward through the slideshow by pressing buttons the person viewing the gallery would control how long they see each slide with the buttons (which may be driven by code?)
Might be worth checking out Adobe's Behance - I don't know much about it admittedly, but it seems to offer slideshow hosting for your work.
Echoing Mylenium - AE is great for making cool content, lacks any way to create interactive content like this. You'll need to look at other apps for the capabilities you're asking for.