Add Comprehensive Security Testing Framework

[famvilianity-eng]

Title: Implement Formal Security Testing Framework with Vulnerability Scanning

Description: Build a comprehensive security testing framework that includes static analysis, fuzzing, and vulnerability scanning, integrated into CI/CD.

Requirements and Context:

• Static analysis: Clippy, Cargo-audit
• Fuzzing: Property-based tests for escrow edge cases
• Dynamic analysis: Test escrow invariants during execution
• Automated vulnerability scanning in CI
• Generate security reports

Suggested Execution: chore/security-testing-framework

Implement Changes:

• Add cargo-audit to CI pipeline
• Implement property-based fuzzing with Quickcheck
• Create /scripts/security-scan.sh for local testing
• Add security test markers and categorization

Test and Commit:

• Run full security test suite locally
• Generate security report from CI run
• Document in /docs/security-testing.md
• Link from CONTRIBUTING.md

Example Commit Message:

chore: add comprehensive security testing framework

- Integrate clippy, cargo-audit in CI pipeline
- Implement property-based fuzzing for escrow invariants
- Add security scan script for local development
- Generate automated security reports

Guidelines:

• Fail CI if security issues found
• Generate SARIF reports for GitHub integration
• Document known vulnerabilities and mitigations

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