fix: use AWS ECR mirror for busybox to avoid Docker Hub rate limits

unification

Release v2.0.0

Simplified shell script-based implementation with improved readiness checks.

BREAKING CHANGES:
- Removed Node.js/TypeScript implementation
- Removed automatic cleanup/post-run functionality
- No build step required

Improvements:
- Intelligent readiness check that handles Helm job retries
- Only verifies essential components (CoreDNS) are running
- Excludes Helm install jobs from failure detection
- Better documentation of background component installation

Update v2 to point to v2.0.0

fix kubectl flag