Refactor: Add FluentAvalonia and remake MainWindow

[d3ara1n]

PR-Codex overview

This PR focuses on refactoring and adding new features to the Chief application.

Detailed summary

• Deleted several files and folders related to the old Chief application structure.
• Added new classes and files for the ViewModel and View components.
• Added new UserControl views for Home, Package, Settings, and Toolchain.
• Added a ViewModelLocator class for dependency injection.
• Added a NavigationService class for navigating between views.
• Updated the App.xaml and App.xaml.cs files for application initialization.
• Added new styles and control themes for Card and HomeView.
• Updated the .gitignore file and added new project files.

The following files were skipped due to too many changes: src/Chief.App/app.manifest, .idea/.idea.Chief/.idea/avalonia.xml, src/Chief.App/MainWindow.axaml, src/Chief.App/Chief.App.csproj, Chief/Program.cs, src/Chief.App/MainWindow.axaml.cs, Chief.sln, .gitignore

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[sonarcloud]

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0.0% Duplication