CI: add least-privilege permissions to GitHub Actions workflows

Add explicit workflow-level permissions blocks to resolve CodeQL
actions/missing-workflow-permissions alerts. Scopes are derived from
workflow operations (git push, artifact upload, Danger, release lanes).

Refs: APPSEC-164

Author: peter-matkovski

.github/workflows/pr-check.yml

@@ -4,6 +4,10 @@ on:
   pull_request:
     types: [opened, edited, synchronize, reopened]
 
+permissions:
+  contents: read
+  pull-requests: read
+
 jobs:
   pr-title:
     name: Validate PR Title