Refactor core logic, add tests, improve CLI and docs
- Split main code into internal services for path, file, transform, rename, and split logic
- Add xUnit test project covering all major features
- Centralize path/namespace resolution with PathLayout record
- Enhance CLI options and help texts for clarity
- Dynamic namespace generation based on output structure
- Refine entity renaming and backup logic
- Update to .NET 10.0, update NuGet packages, add test project to solution
- Revise README.md with new usage and options (Spanish)
- Add InternalsVisibleTo for test access