docs(security): Add PGP Public Key

[Bahati308]

Pull Request Title

Description

Type of Change

• Bug Fix
• New Feature / Enhancement
• Refactor / Code Cleanup
• Documentation Update
• Maintenance / Chore
• Other (please specify):

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Component(s) Affected

• formulus (React Native mobile app)
• formulus-formplayer (React web app)
• synkronus (Go backend server)
• synkronus-cli (Command-line utility)
• Documentation
• DevOps / CI/CD
• Other:

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Related Issue(s)

Closes/Fixes/Resolves:

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Testing

• Unit tests added/updated
• Integration tests added/updated
• Manually tested
• Tested on multiple platforms (if applicable)
• Not applicable

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Breaking Changes

• This PR introduces breaking changes
• This PR does NOT introduce breaking changes

If breaking changes, please describe migration steps:

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Documentation Updates

• Documentation has been updated
• Documentation update is not required

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Checklist

• Code follows project style guidelines
• All existing tests pass
• New tests added for new functionality
• PR title follows Conventional Commits format

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