refactor(server, web, mobile): Change wording of memory titles

[rawcomposition]

On the memory cards, I think the [n] years since... titles should say [n] years ago.

If the caption was above the image, it might make more sense. It would read more like:

15 years since...[this image of me eating pizza]

But because it's a caption over top of the image and positioned at the bottom, your eye goes to the image first, then the caption, and hence it reads more like:

[this image of me eating pizza]. 15 years since...

Which grammatically doesn't make much sense.

I wish I knew enough about Dart to refactor the titles so they use i18n instead of just showing the title value from the JSON response, but I'm completely lost in Dart, unfortunately!