Potential fix for pull request finding 'CodeQL / Workflow does not contain permissions'

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

Author: jkyberneees

.github/workflows/piguard-e2e.yml

@@ -16,6 +16,9 @@ on:
   pull_request:
     branches: [main]
 
+permissions:
+  contents: read
+
 env:
   PIGUARD_MODEL_REVISION: dd78b24e330193a22d2293ac66922dd4f982f563 # keep in sync with docker/piguard/export_onnx.py