[IMPROVEMENT] [BUG?] UnigetUI should remember it's size and position on the desktop

### Please confirm these before moving forward.

- [x] I have searched for my feature proposal and have not found a work-in-progress/duplicate/resolved/discarded issue.
- [x] This improvement refers to an existing feature. If you want to suggest a new feature, please use [this template](https://github.com/Devolutions/UniGetUI/issues/new?labels=new-feature&projects=&template=feature-request.yml&title=%5BFEATURE+REQUEST%5D+%28Enter+your+description+here%29).
- [x] This improvement is not a bug. If you want to report a bug, please use [this template](https://github.com/Devolutions/UniGetUI/issues/new?labels=bug&projects=&template=bug-issue.yml&title=%5BBUG%5D+%28Enter+your+description+here%29).

### Describe the improvement

UnigetUI should remember it's size and position on the desktop.
I _think_ older versions did, but I'm not quite 100% sure.

Currently, it puts itself fairly consistently in a not-too-unreasonable position on autostartup on my desktop PC, which has a 1080P screen. But if I shut it down and then restart it, then it moves.
But on my laptop (which has more pixels but is at 150% scaling and is therefore effectively a smaller size) it tends to position itself too far to the right so that is partly off the screen.

I would prefer it to remember how I positioned it, and if possible, sized it.

### Describe how this improvement could help users

Self explanatory.

No file, test, or entry point is named in the issue. Start by locating the desktop window startup and shutdown handling, then reproduce the behavior on the desktop PC and laptop scenarios described. Done means the application restores its previous position and, where possible, its size without placing the window partly off-screen.

Written by the indexing model from the issue text.