[IMPROVEMENT] (Improve the first launch of the interface for the program)

### 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

When you first launch the program, it opens very wide, which doesn't look very good.
With the transition to Avalonia, the first launch makes it very inconvenient to expand in width, although this is not necessary.

### Describe how this improvement could help users

It will look less terrible when you first launch it.
An example of what the first deployment should look like.

The issue names no source file, test, or entry point. Start by locating the Avalonia startup and window-sizing path, then compare the initial dimensions with the attached examples; done means the first launch no longer opens excessively wide or requires unnecessary manual expansion.

Written by the indexing model from the issue text.