Add Docker support for local and published simulation images

[jlgalanRB]

Summary

This PR adds Docker support for robotnik_simulation so the simulation can now be run in two supported ways:

• from a published Docker image
• from a locally built image generated from this repository

The Docker setup was not previously ready for these workflows end-to-end. With this change, the repository now includes the required Docker configuration plus the updated documentation to use it in practice.

What changed

• added/updated the Docker setup required to run robotnik_simulation in a container
• enabled support for using a published image directly
• enabled support for building the image locally from this repository
• documented that the image copies only robotnik_simulation from the local machine
• documented that additional repositories are imported from dependencies/repos/robotnik_simulation.jazzy.repos
• documented that extra local packages from the host workspace are not included automatically
• documented that any extra repositories required by the image must be declared in dependencies/repos/robotnik_simulation.jazzy.repos
• wired the runtime configuration through env/robot.env
• added the Compose-based launch flow for the simulation container
• documented the practical day-to-day workflow in docker/README.md
• documented how to enter the running container with docker exec to interact with the installed runtime environment
• updated the main README and robotnik_gazebo_ignition/README.md so they point to the current Docker workflow

Why

Until now, the repository did not provide a complete Docker workflow ready to use in practice. This PR makes Docker a supported way to run the simulation, both for local image generation and for execution from a published image, and aligns the documentation with how the container is actually built and used.

Notes

• this PR includes both Docker implementation changes and documentation updates
• runtime simulation options are configured in env/robot.env
• the image copies only robotnik_simulation from the local machine
• additional repositories must be declared in dependencies/repos/robotnik_simulation.jazzy.repos
• extra local packages from the host workspace are not included automatically
• local source changes require rebuilding the image
• the runtime container uses the installed workspace, not a live bind-mounted source workspace