API Server and Documentation

[hsaito]

This pull request introduces a new ASP.NET Core Web API project for My Number validation and generation, updates documentation to reflect the expanded project structure, and adds comprehensive tests for the new API endpoints. It also removes the legacy Dockerfile and updates test dependencies to support xUnit and API testing.

New ASP.NET Core Web API:

• Added MyNumberNET_ApiServer project with a RESTful controller (MyNumberController) exposing endpoints for verifying My Numbers and calculating check digits. (MyNumberNET_ApiServer/Controllers/MyNumberController.cs)
• Implemented API server startup and routing logic in Program.cs. (MyNumberNET_ApiServer/Program.cs)
• Created project file for the API server, targeting .NET 8.0 and referencing the core library. (MyNumberNET_ApiServer/MyNumberNET_ApiServer.csproj)

Testing Enhancements:

• Added xUnit-based tests for the new API controller, covering valid, invalid, and malformed input scenarios. (MyNumberNET_Test/MyNumberControllerTests.cs)
• Updated test project dependencies and references to include xUnit and the API server project. (MyNumberNET_Test/MyNumberNET_Test.csproj)

Documentation and Cleanup:

• Updated README.md to document the new API server, clarify project structure, and improve usage instructions for all components. [1] [2] [3]
• Removed the legacy Dockerfile for .NET Core SDK builds. (Dockerfile)