feat: project setup and core models with TDD

MILESTONE 1 COMPLETE:

Project Setup:
- Create .NET 8 MAUI solution targeting iOS, macOS, and web
- Configure nullable reference types and warnings as errors
- Add required dependencies (MAUI 8.0.3, SQLite, CommunityToolkit.Mvvm)
- Add testing dependencies (xUnit, NSubstitute, FluentAssertions, Coverlet)
- Create comprehensive .editorconfig with C# coding standards
- Update CLAUDE.md with development commands

Core Models (TDD - 48 tests, all passing):
- EstimateMode enum (Work, Generic, Humorous modes)
- EstimateResult model with validation (intensity 0.0-1.0, non-null text)
- ShakeData model with intensity validation
- AppSettings model with defaults (Work mode, max history 10)

Build Status:
- All platforms build successfully (net8.0, iOS, macOS)
- 0 warnings, 0 errors
- Test coverage: 51.28% line, 87.5% branch (models have ~100% coverage)

Per spec: Strict TDD followed (RED-GREEN-REFACTOR), models fully validated

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/HihaArvio/Platforms/Windows/App.xaml

@@ -0,0 +1,8 @@
+<maui:MauiWinUIApplication
+    x:Class="HihaArvio.WinUI.App"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:maui="using:Microsoft.Maui"
+    xmlns:local="using:HihaArvio.WinUI">
+
+</maui:MauiWinUIApplication>

src/HihaArvio/Platforms/Windows/App.xaml.cs

@@ -0,0 +1,24 @@
+using Microsoft.UI.Xaml;
+
+// To learn more about WinUI, the WinUI project structure,
+// and more about our project templates, see: http://aka.ms/winui-project-info.
+
+namespace HihaArvio.WinUI;
+
+/// <summary>
+/// Provides application-specific behavior to supplement the default Application class.
+/// </summary>
+public partial class App : MauiWinUIApplication
+{
+	/// <summary>
+	/// Initializes the singleton application object.  This is the first line of authored code
+	/// executed, and as such is the logical equivalent of main() or WinMain().
+	/// </summary>
+	public App()
+	{
+		this.InitializeComponent();
+	}
+
+	protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();
+}
+

src/HihaArvio/Platforms/Windows/Package.appxmanifest

@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Package
+  xmlns="http://schemas.microsoft.com/appx/manifest/foundation/windows10"
+  xmlns:uap="http://schemas.microsoft.com/appx/manifest/uap/windows10"
+  xmlns:mp="http://schemas.microsoft.com/appx/2014/phone/manifest"
+  xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities"
+  IgnorableNamespaces="uap rescap">
+
+  <Identity Name="maui-package-name-placeholder" Publisher="CN=User Name" Version="0.0.0.0" />
+
+  <mp:PhoneIdentity PhoneProductId="57605B8D-84AE-4E26-B302-7075B28337F9" PhonePublisherId="00000000-0000-0000-0000-000000000000"/>
+
+  <Properties>
+    <DisplayName>$placeholder$</DisplayName>
+    <PublisherDisplayName>User Name</PublisherDisplayName>
+    <Logo>$placeholder$.png</Logo>
+  </Properties>
+
+  <Dependencies>
+    <TargetDeviceFamily Name="Windows.Universal" MinVersion="10.0.17763.0" MaxVersionTested="10.0.19041.0" />
+    <TargetDeviceFamily Name="Windows.Desktop" MinVersion="10.0.17763.0" MaxVersionTested="10.0.19041.0" />
+  </Dependencies>
+
+  <Resources>
+    <Resource Language="x-generate" />
+  </Resources>
+
+  <Applications>
+    <Application Id="App" Executable="$targetnametoken$.exe" EntryPoint="$targetentrypoint$">
+      <uap:VisualElements
+        DisplayName="$placeholder$"
+        Description="$placeholder$"
+        Square150x150Logo="$placeholder$.png"
+        Square44x44Logo="$placeholder$.png"
+        BackgroundColor="transparent">
+        <uap:DefaultTile Square71x71Logo="$placeholder$.png" Wide310x150Logo="$placeholder$.png" Square310x310Logo="$placeholder$.png" />
+        <uap:SplashScreen Image="$placeholder$.png" />
+      </uap:VisualElements>
+    </Application>
+  </Applications>
+
+  <Capabilities>
+    <rescap:Capability Name="runFullTrust" />
+  </Capabilities>
+
+</Package>

src/HihaArvio/Platforms/Windows/app.manifest

@@ -0,0 +1,15 @@
+<?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="HihaArvio.WinUI.app"/>
+
+  <application xmlns="urn:schemas-microsoft-com:asm.v3">
+    <windowsSettings>
+      <!-- The combination of below two tags have the following effect:
+           1) Per-Monitor for >= Windows 10 Anniversary Update
+           2) System < Windows 10 Anniversary Update
+      -->
+      <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>