feat(cmd): Add windsor push command for pushing OCI artifacts

[rmvangun]

Implements the windsor push command to package and publish Windsor blueprints as OCI artifacts to any compatible registry (Docker Hub, GitHub Container Registry, AWS ECR, etc.).

Features

• OCI Registry Support: Push to any - OCI-compatible registry with automatic authentication
• FluxCD Compatibility: Generates artifacts compatible with FluxCD's OCIRepository
• Flexible Tagging: Support for explicit tags or metadata.yaml-driven versioning
• Repository Name Extraction: Automatically extracts repo name from registry URLs

Usage

# Push with explicit tag
windsor push ghcr.io/myorg/myblueprint:v1.0.0

# Push using metadata.yaml for versioning  
windsor push registry.example.com/blueprints