[CHORE] Add cargo-audit to CI pipeline for dependency vulnerability scanning

[ElioNeto]

Description

The CI pipeline (pr-validation.yml) does not run cargo audit to scan dependencies for known security vulnerabilities. Given that ApexStore has 40+ dependencies (including actix-web, tokio, serde, lz4_flex, etc.), unpatched CVEs could go unnoticed.

Proposed fix

Add a cargo-audit step to pr-validation.yml:

audit:
  name: Security Audit
  runs-on: ubuntu-latest
  steps:
    - uses: actions/checkout@v4
    - uses: rustsec/audit-check@v2.0.0
      with:
        token: ${{ secrets.GITHUB_TOKEN }}

Note: rustsec/audit-check requires checks: write permission on the workflow.

Severity

Medium — no known vulnerabilities currently, but no guard against future ones.

Labels

[ElioNeto]

Fixed in commit b6ecb48. Added cargo-audit job to ci.yml using rustsec/audit-check@v2.0.0 with checks: write permission.