[Feature] Clickable movie covers, show full size in lightbox

[sleetx]

Movie covers on the movie page are static images that are not clickable or viewable in full size. I would like to be able to click and open them in lightbox to see the full size, and to scroll between the front and back cover in the lightbox.

A slightly different "mouse-over zoom" feature was mentioned in #398 - but for consistency with other images, I think a lightbox is preferred.