Overview

This PR migrates the repository from the traditional .sln format to the modern .slnx solution file format exclusively, removing the legacy .sln file to avoid CI/CD conflicts.

Changes

• Generated EssentialCSharp.Web.slnx using dotnet sln migrate command
• Removed the traditional EssentialCSharp.Web.sln file to prevent "multiple solution files" errors in CI
• Updated Dockerfile to reference .slnx instead of .sln

Why This Change?

The .slnx format is the modern solution file format introduced in recent .NET SDK versions. It provides:

• Cleaner format: 19 lines vs 63 lines (846 bytes vs 3.8KB)
• Better readability: Human-friendly XML structure
• Forward compatibility: Prepares the repository for future .NET tooling that may prefer or require this format
• CI/CD compatibility: Having only one solution file prevents ambiguity errors when dotnet commands don't specify which solution to use

By using only the .slnx format, we eliminate the MSB1011 error that occurred when multiple solution files were present in the same directory.

Verification

The .slnx solution file has been verified to work correctly:

• ✅ dotnet restore automatically finds and uses the .slnx file
• ✅ dotnet build works without specifying a solution file
• ✅ dotnet test runs successfully (54/55 tests pass - one pre-existing network connectivity test failure)
• ✅ Dockerfile updated to explicitly reference .slnx for Docker builds

References

• Microsoft Documentation: dotnet sln migrate

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