Migrate Platform Utilities #10
Description
Move the utility functions (distro detection, package fetching) to the platform layer. Tasks:
- Create directory internal/platform.
- Move system/utils/detect_distro.go → internal/platform/distro.go.
- Move system/utils/fetch_packages.go → internal/platform/packages.go.
- Rename package from utils to package platform.
- Update imports in all the relevant files.
- Verify go run main.go still works.