Add C# dotnet exact EXI codec implementation

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Co-Authored-By: Claude <noreply@anthropic.com>

csharp/dotnet/Program.cs

@@ -16,7 +16,7 @@ namespace V2GDecoderNet
 {
     class Program
     {
-        static void Main(string[] args)
+        static void MainOriginal(string[] args)
         {
             Console.WriteLine("=== V2GDecoderNet - C# EXI Codec ===");
             Console.WriteLine("OpenV2G C# Port v1.0.0");