Ship as native package

Just opening this up for discussion.
While flatpak is great for a lot of stuff I think it might not be the best fit for a *built in* screenshot tool.

1. Most obvious: permission issues. While we don't have to deal with screenshot permissions yet since we only use the interactive portal we'll have to deal with them at a later point once some upstream changes are merged. The big issue here is that it might be unintuitive that the - once again: *built in* - screenshot app requests permission to take a screenshot. Another thing that might already pose problems is that while we're taking an interactive screenshot we require background permission which if accidentally disabled by the user (because why would a screenshot tool require background permission, it will just suck up my battery) will lead to the app just being killed.
2. Speed: Usually not a problem but flatpaks do have a somewhat noticeable launch time. With normal apps you kinda expect that but with just a screenshot UI you usually expect it to show up immediately (or at least it's much nicer for a quick action like taking a screenshot)
3. There aren't that many drawbacks:
- the app won't be able to be uninstalled
- we are limited to the dependency versions the base systems ships which for an app that doesn't require much should be manageable

Those are just my thoughts lmk what u think (especially the speed thing kinda annoys me even though it's not even a full second lol) :)