Add V2G library project and refactor code structure

- Create V2GProtocol.Library project for DLL usage by external programs
- Add V2GApi.cs with public API methods for EXI encoding/decoding
- Move helper functions to Helper.cs for better code organization
- Update project configuration for .NET Framework 4.8
- Translate all comments in Program.cs to Korean
- Fix .hex file handling to read as binary instead of text

🤖 Generated with [Claude Code](https://claude.ai/code)

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

V2GProtocol.csproj

@@ -5,6 +5,7 @@
     <TargetFramework>net48</TargetFramework>
     <LangVersion>9.0</LangVersion>
     <AssemblyName>V2GDecoder</AssemblyName>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
   </PropertyGroup>
 
   <ItemGroup>