chore(app): scaffold Avalonia application project

src/Vantage.App/App.axaml

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+<Application xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             x:Class="Vantage.App.App"
+             RequestedThemeVariant="Dark">
+
+  <Application.Styles>
+    <FluentTheme />
+
+    <Style Selector="Border.card">
+      <Setter Property="Background" Value="{DynamicResource SurfaceBrush}" />
+      <Setter Property="CornerRadius" Value="8" />
+      <Setter Property="Padding" Value="14" />
+      <Setter Property="BorderBrush" Value="#2C323D" />
+      <Setter Property="BorderThickness" Value="1" />
+    </Style>
+  </Application.Styles>
+
+  <Application.Resources>
+    <ResourceDictionary>
+      <SolidColorBrush x:Key="AccentBrush" Color="#4FC3F7" />
+      <SolidColorBrush x:Key="OkBrush" Color="#4CAF50" />
+      <SolidColorBrush x:Key="WarnBrush" Color="#FFB300" />
+      <SolidColorBrush x:Key="DownBrush" Color="#EF5350" />
+      <SolidColorBrush x:Key="SurfaceBrush" Color="#1B1F27" />
+      <SolidColorBrush x:Key="SurfaceAltBrush" Color="#232833" />
+    </ResourceDictionary>
+  </Application.Resources>
+
+</Application>

src/Vantage.App/App.axaml.cs

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+using Avalonia;
+using Avalonia.Controls.ApplicationLifetimes;
+using Avalonia.Markup.Xaml;
+using Microsoft.Extensions.DependencyInjection;
+using Vantage.App.ViewModels;
+using Vantage.App.Views;
+
+namespace Vantage.App;
+
+public partial class App : Application
+{
+    public override void Initialize() => AvaloniaXamlLoader.Load(this);
+
+    public override void OnFrameworkInitializationCompleted()
+    {
+        var services = new ServiceCollection();
+        services.AddVantageApp(VantageAppServices.ResolveProviderMode());
+        var provider = services.BuildServiceProvider();
+
+        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
+        {
+            var viewModel = provider.GetRequiredService<MainWindowViewModel>();
+            desktop.MainWindow = new MainWindow { DataContext = viewModel };
+            desktop.ShutdownRequested += (_, _) => viewModel.StopMonitoring();
+            _ = StartAsync(viewModel);
+        }
+
+        base.OnFrameworkInitializationCompleted();
+    }
+
+    private static async Task StartAsync(MainWindowViewModel viewModel)
+    {
+        await viewModel.InitializeAsync();
+        viewModel.StartMonitoring();
+    }
+}

src/Vantage.App/Program.cs

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+using Avalonia;
+
+namespace Vantage.App;
+
+internal static class Program
+{
+    [STAThread]
+    public static void Main(string[] args) => BuildAvaloniaApp()
+        .StartWithClassicDesktopLifetime(args);
+
+    public static AppBuilder BuildAvaloniaApp() => AppBuilder
+        .Configure<App>()
+        .UsePlatformDetect()
+        .WithInterFont()
+        .LogToTrace();
+}

src/Vantage.App/Vantage.App.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <LangVersion>latest</LangVersion>
+    <BuiltInComInteropSupport>true</BuiltInComInteropSupport>
+    <ApplicationManifest>app.manifest</ApplicationManifest>
+    <AvaloniaUseCompiledBindingsByDefault>true</AvaloniaUseCompiledBindingsByDefault>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <AvaloniaResource Include="Assets/**" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Avalonia" Version="11.0.10" />
+    <PackageReference Include="Avalonia.Desktop" Version="11.0.10" />
+    <PackageReference Include="Avalonia.Themes.Fluent" Version="11.0.10" />
+    <PackageReference Include="Avalonia.Fonts.Inter" Version="11.0.10" />
+    <PackageReference Include="Avalonia.Diagnostics" Version="11.0.10" Condition="'$(Configuration)' == 'Debug'" />
+    <PackageReference Include="CommunityToolkit.Mvvm" Version="8.2.2" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.1" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Vantage.Core\Vantage.Core.csproj" />
+  </ItemGroup>
+
+</Project>

src/Vantage.App/app.manifest

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+<?xml version="1.0" encoding="utf-8"?>
+<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
+  <assemblyIdentity version="1.0.0.0" name="Vantage.App" />
+
+  <application xmlns="urn:schemas-microsoft-com:asm.v3">
+    <windowsSettings>
+      <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">true/pm</dpiAware>
+      <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">permonitorv2,permonitor</dpiAwareness>
+    </windowsSettings>
+  </application>
+</assembly>