Add dotnet-tools.json and publish script for .NET 8

Added a `dotnet-tools.json` file to define a .NET tool manifest, specifying the `dotnet-ef` tool with version `10.0.9`.

Introduced a `publish.bat` script for publishing the `EnvelopeGenerator.Server` project as a self-contained application targeting `win-x64` and .NET 8. The script handles cleaning, publishing, output verification, and provides deployment instructions for IIS.

Updated the `EnvelopeGenerator.sln` file to include a reference to the `publish.bat` script under the `EnvelopeGenerator.Server` project using a `SolutionItems` section.

EnvelopeGenerator.Server/EnvelopeGenerator.Server/dotnet-tools.json

@@ -0,0 +1,13 @@
+{
+  "version": 1,
+  "isRoot": true,
+  "tools": {
+    "dotnet-ef": {
+      "version": "10.0.9",
+      "commands": [
+        "dotnet-ef"
+      ],
+      "rollForward": false
+    }
+  }
+}