v0.2.0

Release v0.2.0: CLI Self-Management

New Features:
- contui update: Self-update to latest version
- contui update --check: Check for updates
- contui uninstall: Uninstall contui
- contui uninstall --purge: Uninstall with config removal
- contui version: Show detailed version info

Improvements:
- CI optimized to only run on main/PRs

Binaries available for:
- Linux x86_64
- macOS x86_64
- macOS aarch64 (Apple Silicon)
- Windows x86_64