HTML pages can be generated server-side. I happen to have developed a portfolio in PHP in the past. There's some optional JavaScript to make it smoother by avoiding unnecessary a page reload for each picture, but it works without (by reloading the page).

Unfortunately, it requires some extra work but I think it's worth it. The rendering part is not duplicated though, there just needs to be some JS code intercepting links being followed and downloading the updated part from the server.