chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/docker-publish.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up QEMU (for multi-arch builds)
         uses: docker/setup-qemu-action@v3