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/ci.yml

@@ -6,6 +6,11 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.head_ref }}
   cancel-in-progress: true
 
+permissions:
+  actions: write
+  contents: read
+  pull-requests: read
+
 jobs:
   build:
     name: 🧪 Test & lint