fix: add pull:true to docker-build to ensure fresh base images

Ensures all Docker builds pull fresh Alpine base images to get
security patches like c-ares 1.34.6-r0 (CVE-2025-62408).

This mirrors the change made to security-weekly-rebuild.yml.

.github/workflows/docker-build.yml

@@ -110,6 +110,7 @@ jobs:
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          pull: true  # Always pull fresh base images to get latest security patches
           cache-from: type=gha
           cache-to: type=gha,mode=max
           build-args: |