Update support status for versions in SECURITY.md

[ghimiresdp]

Description

Add security policy to document supported versions for automated repository security checks.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation
• Performance improvement

Checklist

• I have run cargo fmt to ensure consistent code style.
• I have run cargo test and all tests passed.
• I have added new tests that prove my fix is effective or that my feature works.
• I have updated the README.md (if applicable).

Performance Impact

[Copilot]

Pull request overview

This PR adds a SECURITY.md file intended to document supported versions and vulnerability reporting procedures. However, the file is the unmodified GitHub default template.

Changes:

• Added a new SECURITY.md with placeholder content (template versions 5.1.x/5.0.x/4.0.x instead of actual project version 0.6.0, and generic instructions instead of real reporting details)

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