Enhacement on security

[susanachl]

Description

This pull request provides a comprehensive update to make the dicom_to_ros project fully compatible with ROS 2 Jazzy and its updated security (SROS2) framework.

This PR addresses the entire lifecycle of the application, including:

• Security Generation: Completely overhauls the generate_keystore.sh script and permissions.xml policy file to align with the modern SROS2 workflow in Jazzy.
• Node Launch: Updates the ROS 2 launch file to correctly map nodes to their security enclave and namespace, preventing startup crashes.
• Documentation: Rewrites the README.md and demo instructions to provide clear, accurate steps for running and extending the secure pipeline.
• CI/CD: Enhances the GitHub Actions workflow to run tests with security enabled.

Related Issue

This code contribution must be associated with an existing issue.
Fixes #22

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Documentation update

How Has This Been Tested?

• Test Configuration: (e.g., ROS 2 Humble, specific sample DICOM files used)

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Contributor Checklist:

• My code follows the ROS 2 code style guidelines for Python.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new linters/syntax warnings.
• I have added regression tests (for bug fixes) or unit tests (for new features) that prove my fix is effective or that my feature works.
• Developer Certificate of Origin (DCO): I have signed-off every commit in this PR by adding Signed-off-by: Name susana.chavez@ekumenlabs.com to the commit messages.