Added CI and Docker workflow

[byteshiftlabs]

Summary:

• Added a more complete CI workflow for gates so GitHub Actions builds, tests, validates docs, runs cppcheck, and checks the Docker image.
• Added Docker-based project setup so the repo can be built and validated in a reproducible Ubuntu 24.04 environment.

Changes:

• Updated the GitHub Actions workflow to use ubuntu-24.04, workflow_dispatch, concurrency control, explicit dependency installation, executable smoke tests, docs artifact upload, and Docker image validation.
• Added a Dockerfile for local and CI builds plus a .dockerignore to keep the Docker context small.
• Added README instructions for Docker-based development and validation.

Testing:

• Ran cmake -S . -B build-ci -DENABLE_TESTING=ON
• Ran cmake --build build-ci --target gates_tests -j2
• Ran ctest --test-dir build-ci --output-on-failure
• Ran cmake --build build-ci --target gates -j2
• Ran ./build-ci/gates --version
• Ran ./build-ci/gates examples/example.c /tmp/example.vhdl
• Ran ./build_docs.sh
• Ran cmake --build build-ci --target cppcheck
• Docker build step was added to CI but could not be executed locally because Docker is not installed in this container.