feat: add Docker Hub authentication for Docker Scout

- Add optional Docker Hub login for enhanced vulnerability data
- Use continue-on-error to make Docker Hub auth optional
- Requires DOCKERHUB_USERNAME and DOCKERHUB_TOKEN secrets for full functionality

.github/workflows/docker-build.yml

@@ -54,6 +54,15 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
+      # Login to Docker Hub for Docker Scout (optional - provides better vulnerability data)
+      # Add DOCKERHUB_USERNAME and DOCKERHUB_TOKEN secrets to enable this
+      - name: Log into Docker Hub
+        uses: docker/login-action@v3
+        continue-on-error: true
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
       # Extract version from tag if present
       - name: Extract version from tag
         id: tag_version