Relocate test project: test/yavscTests -> src/Yavsc.Org.Tests

Move the integration test project from the top-level test/ directory into
src/ alongside the projects it tests. Rename the project (and folder) to
Yavsc.Org.Tests to match .NET conventions and reflect that it tests the
Org runtime primarily.

Path changes:
- test/yavscTests/yavscTests.csproj -> src/Yavsc.Org.Tests/Yavsc.Org.Tests.csproj
- All .cs / .json / .resx files moved to their new location
- PostItViewModelTests moved out to the dedicated src/PostIt.Tests project
  (it was unrelated to Org testing)

Build adjustments:
- <ProjectReference> paths shortened (..\..\src\X -> ..\X)
- PostIt project reference removed (covered by its own test project)
- <OutputType>exe added (required by xunit.v3)
- xunit.v3.common and xunit.v3.extensibility.core added to package versions

Solution + sln:
- yavsc.sln Project Name updated to 'Yavsc.Org.Tests' and path updated
- GUID preserved so existing build configs stay valid

Static web assets:
- The CopyStaticWebAssetsManifest target was hard-coding the destination
  filename to 'testhost.staticwebassets.endpoints.json', which worked
  when the assembly was named 'yavscTests'. Now that the assembly name
  is 'Yavsc.Org.Tests', ASP.NET Core's MapStaticAssets() looks for
  'Yavsc.Org.Tests.staticwebassets.endpoints.json' (entry-assembly-based
  resolution). Use $(MSBuildProjectName) so the copy target stays
  correct under any future rename.

src/Yavsc.Org.Tests/Yavsc.Org.Tests.csproj

@@ -0,0 +1,55 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+    <RootNamespace>Yavsc.Tests</RootNamespace>
+    <UserSecretsId>78a4efec-68dc-4745-ba06-d8545ef9ee91</UserSecretsId>
+    <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
+    <OutputType>exe</OutputType>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Design">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="IdentityModel.OidcClient" />
+    <PackageReference Include="Selenium.WebDriver" />
+    <PackageReference Include="Microsoft.AspNetCore.Hosting" />
+    <PackageReference Include="Microsoft.Extensions.Caching.Memory" />
+    <PackageReference Include="Microsoft.Extensions.Options" />
+    <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" />
+    <PackageReference Include="xunit.v3" />
+    <PackageReference Include="xunit.v3.common" />
+    <PackageReference Include="xunit.v3.extensibility.core" />
+    
+    <PackageReference Include="xunit.runner.visualstudio" />
+  </ItemGroup>
+  <ItemGroup>
+    <Content Include="appsettings.json">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+  <ItemGroup>
+    <Content Include="appsettings.*.json">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\Yavsc.Org\Yavsc.Org.csproj" />
+    <ProjectReference Include="..\Yavsc.Abstract\Yavsc.Abstract.csproj" />
+    <ProjectReference Include="..\Yavsc.Server\Yavsc.Server.csproj" />
+  </ItemGroup>
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" />
+  </ItemGroup>
+  <Target Name="CopyStaticWebAssetsManifest" AfterTargets="Build">
+    <Copy SourceFiles="$(OutDir)Yavsc.Org.staticwebassets.endpoints.json" DestinationFiles="$(OutDir)$(MSBuildProjectName).staticwebassets.endpoints.json" SkipUnchangedFiles="true" Condition="Exists('$(OutDir)Yavsc.Org.staticwebassets.endpoints.json')" />
+  </Target>
+</Project>