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/NonRegression/EMailling.cs

@@ -0,0 +1,43 @@
+
+using yavscTests.ServerFixtures;
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Yavsc.Interface;
+
+namespace yavscTests
+{
+
+    [Collection("EMaillingTeststCollection")]
+    [Trait("regression", "II")]
+    public class EMaillingTests : IClassFixture<WebServerFixture>
+
+    {
+        readonly WebServerFixture _serverFixture;
+        readonly ITestOutputHelper output;
+        readonly ILogger _logger;
+        public EMaillingTests(WebServerFixture serverFixture, ITestOutputHelper output)
+        {
+            this.output = output;
+            _serverFixture = serverFixture;
+            _logger = serverFixture.Logger;
+        }
+
+        [Fact]
+        public void SendEMailSynchrone()
+        {
+
+            using IServiceScope scope = _serverFixture.Services.CreateScope();
+            ITrueEmailSender mailSender = scope.ServiceProvider.GetRequiredService<ITrueEmailSender>();
+
+            output.WriteLine("SendEMailSynchrone ...");
+            mailSender.SendEmailAsync
+          (
+            _serverFixture.SiteSettings.Owner.Name,
+            _serverFixture.SiteSettings.Owner.EMail,
+            $"monthly email",
+            "test boby monthly email").Wait();
+
+        }
+    }
+}