[Phase 5.1] Add container deployment configuration

[loonghao]

Parent Issue

Part of #273 - .vx.toml v2 Configuration Enhancement

Objective

Add container deployment configuration for Docker/Podman builds and registry management.

Configuration Format

[container]
enabled = true
runtime = "docker"  # docker | podman | containerd

[container.build]
dockerfile = "Dockerfile"
context = "."
target = "production"
args = { NODE_ENV = "production" }

[container.registry]
url = "ghcr.io"
username = "${GITHUB_ACTOR}"
password = "${GITHUB_TOKEN}"

[container.compose]
file = "docker-compose.yml"
profiles = ["dev", "test", "prod"]

Tasks

• Define ContainerConfig structure
• Implement vx container build command
• Implement vx container push command
• Add multi-stage build support
• Add registry authentication
• Generate Dockerfile from config
• Add docker-compose integration
• Add unit tests

Commands

vx container build         # Build container image
vx container push          # Push to registry
vx container run           # Run container locally
vx container export        # Generate Dockerfile

Acceptance Criteria

• Container builds successfully
• Push to registry works
• Multi-stage builds supported
• Generated Dockerfile is valid