Docker implementation [skip windows]

[Jrice1317]

Description

This PR adds Docker output support to constructor, generating a ready-to-use Dockerfile and optionally building the resulting image via installer_type: docker and docker_build: true in the construct.yaml.

Changes

New:

• constructor/docker_build.py: Handles Docker output by rendering template and optionally building image
• constructor/dockerfile_template.tmpl: Template used to generate Dockerfile
• examples/docker_build/construct.yaml: Example construct.yaml used for testing

Updated:

• constructor/_schema.py: Adds docker to installer_type and adds docker_base_image, docker_tag, docker_labels
• constructor/main.py: Adds docker to installer types
• tests/test_examples.py: Adds test_docker_build to cover Dockerfile generation, image build and smoke test

Notes:

• Verified RuntimeError is raised when base_image is not provided

RuntimeError: Base image for Dockerfile not specified. Please set 'docker_base_image' in construct.yaml, e.g.:
 docker_base_image: debian:13.4-slim@sha256:4ffb3a1511099754cddc70eb1b12e50ffdb67619aa0ab6c13fcd800a78ef7c7a

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?