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/Android/AndroidManifest.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+	<application android:allowBackup="true" android:icon="@mipmap/appicon" android:roundIcon="@mipmap/appicon_round" android:supportsRtl="true"></application>
+	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+	<uses-permission android:name="android.permission.INTERNET" />
+</manifest>

src/HihaArvio/Platforms/Android/MainActivity.cs

@@ -0,0 +1,10 @@
+using Android.App;
+using Android.Content.PM;
+using Android.OS;
+
+namespace HihaArvio;
+
+[Activity(Theme = "@style/Maui.SplashTheme", MainLauncher = true, LaunchMode = LaunchMode.SingleTop, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize | ConfigChanges.Density)]
+public class MainActivity : MauiAppCompatActivity
+{
+}

src/HihaArvio/Platforms/Android/MainApplication.cs

@@ -0,0 +1,15 @@
+using Android.App;
+using Android.Runtime;
+
+namespace HihaArvio;
+
+[Application]
+public class MainApplication : MauiApplication
+{
+	public MainApplication(IntPtr handle, JniHandleOwnership ownership)
+		: base(handle, ownership)
+	{
+	}
+
+	protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();
+}

src/HihaArvio/Platforms/Android/Resources/values/colors.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="colorPrimary">#512BD4</color>
+    <color name="colorPrimaryDark">#2B0B98</color>
+    <color name="colorAccent">#2B0B98</color>
+</resources>