Refactor: split Program.cs into Menu, Output, DTO
Refactored the benchmark console app for modularity:
- Moved all menu logic to Menu.cs (main/settings menus)
- Moved all output/result formatting to Output.cs
- Extracted BenchmarkResult DTO to BenchmarkResult.cs
- Program.cs now only handles orchestration and the benchmark loop
- Moved GetCurrentCharsetName to Configuration.cs
- Removed obsolete Warmup methods from serializers
No functional changes; improves clarity and maintainability.
