[FEATURE] Add ghostcheck version subcommand with environment info

[KbWen]

Feature Description

Currently, GhostCheck only supports ghostcheck --version as a flag. Many modern CLI tools also support ghostcheck version as a subcommand (similar to docker version, npm version, go version).

Why This Matters

• More discoverable for new users who type ghostcheck version intuitively
• Consistent with CLI UX conventions
• The subcommand form can later be extended to show richer info (Python version, installed plugins, config file paths, etc.)

Proposed Implementation

1. Add a version subparser in cli.py
2. When invoked, print version info and optionally Python version + platform info
3. Example output:

GhostCheck v1.1.0
Python 3.12.0
Platform: Windows-11-10.0.22631-SP0
Config: ghostcheck.toml (found)
Preset: auto-detected (generic)