Improve theming and layout for the Settings window and related services.
- MaterialSurfaceService: add special material parameters for SettingsWindowBackground (lower alpha, no blur) and avoid hot-switching real backdrops for non-settings windows.
- GlassEffectService: add AdaptiveSettingsWindowTintBrush + ResolveSettingsWindowTintAlpha to provide optional content tinting tied to system material mode.
- SettingsWindowService: refactor theme application into ApplyThemeVariantAndResources, ensure settings window material is applied at show/activate times, and tidy theme/resource application flow.
- SettingsWindow.axaml / .axaml.cs: restructure title bar (separate Grid.Row=0 border) and FANavigationView host, add pane-footer toggle button for :minimal layout, use dynamic corner radius resource, and update toggle/visibility/icon logic and responsive layout code.
- SettingsPages: remove some IconText usages and adjust margins; use DesignCornerRadiusLg for update card corner radius.
- Add NuGet.Config to set local globalPackagesFolder and ignore .nuget/packages in .gitignore.
These changes aim to improve visuals, avoid backdrop overdraw, and make the settings window behavior consistent across themes and layouts.
