UI button to lock pan/zoom

[deckerst]

Discussed in https://github.com/deckerst/aves/discussions/1182

^{Originally posted by AeliusSaionji September 12, 2024} I often need to zoom in on a picture to see if small details are in focus. If I take multiple similar shots, it would be convenient to be able to swipe between them to compare a zoomed-in section of the image.

This would be particularly useful for burst shots, too.

I would imagine we'd want the lock button to reset every time we leave Aves, so normal function is always default.