It turns out my unlimited hosting account was not as unlimited as I'd thought. In particular, it's "not intended to be used for data backup or archiving purposes." And 20-plus years and a quarter-terabyte of photos is clearly an archive of my own.
So I'm learning how I can rebuild the Gallery within my hosting service's rules. It's going to be a process, but we'll get there.
I want the new version to be smartphone-friendly. To that end, if you know of any photo-oriented websites that you think work particularly well on your mobile, I'd like to hear about them and what you like about them.
You probably know where to find me...