changes to the remote execution of the release

.github/workflows/release-docker.yml

@@ -26,7 +26,7 @@ env:
 jobs:
   release-docker:
     # Hinweis: Falls dein lokaler Gitea-Runner ein anderes Label hat (z.B. 'linux' oder 'self-hosted'), passe dies hier an.
-    runs-on: linux
+    runs-on: ubuntu-latest
 
     steps:
       - name: Checkout
@@ -118,6 +118,23 @@ jobs:
           echo "image=$IMAGE" >> "$GITHUB_OUTPUT"
           echo "lower_repo=$LOWER_REPO" >> "$GITHUB_OUTPUT"
 
+      - name: Ensure Docker CLI is available
+        run: |
+          if command -v docker >/dev/null 2>&1; then
+            docker --version
+            exit 0
+          fi
+
+          if command -v apt-get >/dev/null 2>&1; then
+            apt-get update
+            DEBIAN_FRONTEND=noninteractive apt-get install -y docker.io
+          elif command -v apk >/dev/null 2>&1; then
+            apk add --no-cache docker-cli
+          else
+            echo "Error: no supported package manager found to install docker"
+            exit 1
+          fi
+
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3