Refactor solution structure and update package version

Updated the Visual Studio solution file to remove obsolete project configuration lines, indicating a cleanup.
The `Microsoft.SemanticKernel` package version has been upgraded from `1.60.0` to `1.61.0`.
Introduced a new solution file format (`SqlDatabaseVectorSearch.slnx`) to better organize solution items in a structured XML format.

Author: marcominerva

SqlDatabaseVectorSearch.sln

@@ -0,0 +1,9 @@
+<Solution>
+  <Folder Name="/Solution Items/">
+    <File Path=".editorconfig" />
+    <File Path=".github/copilot-instructions.md" />
+    <File Path="Directory.Build.props" />
+    <File Path="README.md" />
+  </Folder>
+  <Project Path="SqlDatabaseVectorSearch/SqlDatabaseVectorSearch.csproj" />
+</Solution>

SqlDatabaseVectorSearch.slnx

@@ -24,7 +24,7 @@
         <PackageReference Include="Microsoft.ML.Tokenizers" Version="1.0.2" />
         <PackageReference Include="Microsoft.ML.Tokenizers.Data.Cl100kBase" Version="1.0.2" />
         <PackageReference Include="Microsoft.ML.Tokenizers.Data.O200kBase" Version="1.0.2" />
-        <PackageReference Include="Microsoft.SemanticKernel" Version="1.60.0" />
+        <PackageReference Include="Microsoft.SemanticKernel" Version="1.61.0" />
         <PackageReference Include="MimeMapping" Version="3.1.0" />
         <PackageReference Include="MinimalHelpers.FluentValidation" Version="1.1.4" />
         <PackageReference Include="MinimalHelpers.Routing.Analyzers" Version="1.1.3" />