Pin dependencies (#29946)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/netlify.yaml

@@ -28,7 +28,7 @@ jobs:
                       Exercise caution. Use test accounts.
 
             - name: 📥 Download artifact
-              uses: actions/download-artifact@v4
+              uses: actions/download-artifact@d3f86a106a0bac45b974a628896c90dbdf5c8093 # v4
               with:
                   github-token: ${{ secrets.GITHUB_TOKEN }}
                   run-id: ${{ github.event.workflow_run.id }}
@@ -36,7 +36,7 @@ jobs:
                   path: webapp
 
             - name: 📤 Deploy to Netlify
-              uses: matrix-org/netlify-pr-preview@v3
+              uses: matrix-org/netlify-pr-preview@9805cd123fc9a7e421e35340a05e1ebc5dee46b5 # v3
               with:
                   path: webapp
                   owner: ${{ github.event.workflow_run.head_repository.owner.login }}