fix(ci): add npm caching to security.yml npm-audit job

Add cache: npm with matrix-based cache-dependency-path to setup-node for consistency with ci.yml and benchmark.yml

Author: ebenezershadrack123-star

.github/workflows/security.yml

@@ -102,6 +102,8 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '18'
+          cache: 'npm'
+          cache-dependency-path: ${{ matrix.package }}/package-lock.json
 
       - name: Audit ${{ matrix.package }} (high/critical)
         continue-on-error: true