feat: Rearrange nix workflow and add docker status check

- The docker status check has been added to check the docker service before a build.
- The build command in the nix workflow has been moved after the docker status check for better error handling.

.forgejo/workflows/nix.yaml

@@ -4,12 +4,15 @@ jobs:
     runs-on: nix
     steps:
       - uses: actions/checkout@v3
-      - run: nix build -L .#runner
       - name: upload image
         run: |
           echo $PATH
           which docker
           ls -al /bin
+          docker status
+      - run: nix build -L .#runner
+      - name: upload image
+        run: |
           docker login -u ${{ secrets.REG_USER }} -p ${{ secrets.REG_TOKEN }} ${{ secrets.CI_REGISTRY }}
           export IMAGE_TAG=$(docker load -i result | grep -Po 'Loaded image.*: \K.*')
           echo "Pushing image ${IMAGE_TAG}"