Update empty state images

[Gabriel Dufresne (GabrielDuf)]

This pull request introduces a new value converter for responsive image scaling, updates empty state visuals, and refines the handling of images and resources in the packages pages. The key improvements are the addition of the ScaleClampConverter for adaptive UI scaling, replacement of several placeholder images with new assets, and updates to XAML to utilize these changes.

UI Responsiveness and Scaling:

• Added a new ScaleClampConverter (src/UniGetUI.Avalonia/Converters/ScaleClampConverter.cs) that enables images to scale proportionally with their container size while respecting a maximum size, improving the adaptability of the UI on different screen sizes.
• Updated AbstractPackagesPage.axaml to use the new converter for MaxWidth and MaxHeight bindings on images, ensuring visuals remain responsive.

Visual and Asset Updates:

• Replaced old empty state images with new themed assets in both the SoftwareUpdatesPage and PackageBundlesPage for a more modern look (Trophee.png and Empty_inbox.png).
• Updated the image shown during loading in AbstractPackagesPage.axaml from jetpack_Maurice2-blue.png to the new launcher.png asset.
• Adjusted project resource references: removed unused images and added new ones in the project file.

XAML and Layout Improvements:

• Registered the new converter as a resource in AbstractPackagesPage.axaml and updated image bindings to use it.
• Added a x:Name to the Panel hosting the package list to enable element binding for responsive sizing.