chore: add security scanning with OSV-Scanner and Bandit

[officialankan]

Description

Adds comprehensive security scanning to the project using OSV-Scanner for dependency vulnerabilities and Bandit for code security analysis.

Changes

• Add workflow with:
  • OSV-Scanner for dependency vulnerability scanning
  • Bandit for Python code security analysis
  • SARIF uploads to GitHub Security tab
  • Runs on PRs, pushes, and weekly schedule
• Add security badges to README.md (Bandit + workflow status)

Related Issue

Closes #36

Testing

• Security workflow will run automatically on this PR
• Verify SARIF results appear in GitHub Security tab
• Confirm badges display correctly in README

Checklist

• Code follows project style guidelines
• Documentation updated (README badges)
• No breaking changes

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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