Initial restructure of image viewer, fixes some immedate bugs

[CTalvio]

trafficstars

Pull Request Description

Starting work on the image viewer. Here is an initial take of on a refactor that works around some of the quirks of extendedimage.

I used a stack to make the image viewer widget the size of the screen, which seems to be the only way to avoid the bugs the current viewer is suffering from.

Hence the scaffold and appbar get ditched in favor of simple containers for any buttons we need, stacked atop the image.

I found that layoutInsets can be used to have the initial size of the image limited to the are that is not covered by buttons.

Issue Being Fixed

The inability of the image to fill the screen in some circumstances, causing it to get cut off for seemingly no reason. This was especially prevalent in landscape aspect ratios.

• #652

Screenshots / Recordings

https://github.com/thunder-app/thunder/assets/4365015/545e0827-c82d-4997-87c6-df29d4681d94

Checklist

• [ ] Did you update CHANGELOG.md?
• [ ] Did you use localized strings where applicable?
• [ ] Did you add semanticLabels where applicable for accessibility?

[CTalvio]

gonna investigate how this handles system padding (notches, softkeys etc.)

[CTalvio]

Ok, the image viewer is now in a really good place I think. Not massively different but now it doesn't seem to suffer from any "quirks".