security: add missing permissions to cache-management workflow

- Add contents: read permission to generate-cache-key job
- Follows principle of least privilege for GitHub Actions
- Addresses CodeQL workflow permissions warning

Author: fgogolli

.github/workflows/cache-management.yml

@@ -28,6 +28,8 @@ jobs:
   generate-cache-key:
     name: Generate Cache Key
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
     outputs:
       cache-key: ${{ steps.cache-key.outputs.key }}
       cache-hit: ${{ steps.cache.outputs.cache-hit }}