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/Mandatory/BatchTests.cs

@@ -0,0 +1,67 @@
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Yavsc.Models;
+using Yavsc.Server.Models.IT.SourceCode;
+using Microsoft.EntityFrameworkCore;
+
+using yavscTests.ServerFixtures;
+using Yavsc.Server.Models.IT;
+
+namespace yavscTests
+{
+    [Collection("Yavsc Server")]
+    [Trait("regression", "oui")]
+    public class BaseTestContext:  IClassFixture<WebServerFixture>, IDisposable
+    {
+        public readonly WebServerFixture _serverFixture;
+        private readonly ITestOutputHelper _output;
+
+        public BaseTestContext(ITestOutputHelper output, WebServerFixture fixture)
+        {
+            this._serverFixture = fixture;
+            this._output = output;
+        }
+
+        // FIXME write a scenario from an empty database [Fact]
+        public void GitClone()
+        {
+            using var scope = _serverFixture.Services.CreateScope();
+            var dbContext = scope.ServiceProvider.GetRequiredService<ApplicationDbContext>();
+            Assert.NotNull(dbContext.Project);
+            Project yavsc = new Project
+            {
+                Name = "Yavsc"
+            };
+            dbContext.Project.Add(yavsc);
+            dbContext.SaveChanges();
+            var firstProject = dbContext.Project.Include(p => p.Repository).FirstOrDefault(
+                p => p.Name == "Yavsc"
+            );
+            Assert.NotNull (firstProject);
+            var di = new DirectoryInfo(_serverFixture.SiteSettings.GitRepository);
+            if (!di.Exists) di.Create();
+
+            var clone = new GitClone(_serverFixture.SiteSettings.GitRepository);
+            clone.Launch(firstProject);
+            gitRepo = di.FullName;
+        }
+        string gitRepo=null;
+        private IConfigurationRoot configurationRoot;
+
+
+        [Fact]
+        public void HaveConfigurationRoot()
+        {
+            var builder = new ConfigurationBuilder();
+            configurationRoot = builder.Build();
+        }
+
+        public void Dispose()
+        {
+            if (gitRepo!=null)
+            {
+                Directory.Delete(Path.Combine(gitRepo,"yavsc"), true);
+            }
+        }
+    }
+}