refactor(m0): restructure project and install dependencies

- Clean Avalonia template content (ViewLocator, greeting, empty Models folder)
- Add YKanBan.Tests (MSTest 4.4.1) to solution
- Install packages per plan version table (Semi.Avalonia, Lucide icons,
  Microsoft.Data.Sqlite, Pidgin, Newtonsoft.Json 13.0.4 fallback)

YKanBan.Tests/YKanBan.Tests.csproj

@@ -0,0 +1,16 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="MSTest" Version="4.4.1" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\YKanBan\YKanBan.csproj" />
+  </ItemGroup>
+</Project>