fix: replace Skopeo push with redhat-actions/push-to-registry

Avoids double compression (chunkah zstd + Skopeo zstd:chunked).
push-to-registry handles auth and multi-tag push natively.

.github/workflows/build.yml

@@ -127,29 +127,20 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
-      # OPTIMIERUNG 2: Skopeo zwingen, die Layer intelligent zu zerteilen
+      - name: Push to GHCR
-      - name: Push to GHCR via Skopeo (with intelligent zstd:chunked rechunking)
+        if: github.event_name != 'pull_request' && github.ref == format('refs/heads/{0}', github.event.repository.default_branch)
+        uses: redhat-actions/push-to-registry@v2
+        with:
+          image: ${{ env.IMAGE_NAME }}
+          tags: ${{ steps.metadata.outputs.tags }}
+          registry: ${{ env.IMAGE_REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Get registry digest
         if: github.event_name != 'pull_request' && github.ref == format('refs/heads/{0}', github.event.repository.default_branch)
         run: |
-          set -x
+          FINAL_REGISTRY_DIGEST=$(skopeo inspect docker://${{ env.IMAGE_REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.DEFAULT_TAG }} --format '{{.Digest}}')
-          
-          export REGISTRY_AUTH_FILE=$HOME/.docker/config.json
-          REGISTRY_PATH="${{ env.IMAGE_REGISTRY }}/${{ env.IMAGE_NAME }}"
-
-          # "zstd:chunked" mit Feineinstellung zwingt Skopeo, Pakete anhand ihrer 
-          # Metadaten (sofern vorhanden) in reproduzierbare Chunks zu brechen.
-          podman unshare bash -c "
-            for tag in ${{ steps.metadata.outputs.tags }}; do
-              skopeo copy \
-                --dest-compress-format=zstd:chunked \
-                --dest-compress-level=5 \
-                --dest-oci-accept-uncompressed-layers \
-                containers-storage:localhost/${{ env.IMAGE_NAME }}:${{ env.DEFAULT_TAG }} \
-                docker://$REGISTRY_PATH:\$tag
-            done
-          "
-
-          FINAL_REGISTRY_DIGEST=$(skopeo inspect docker://$REGISTRY_PATH:${{ env.DEFAULT_TAG }} --format '{{.Digest}}')
           echo "REGISTRY_DIGEST=$FINAL_REGISTRY_DIGEST" >> $GITHUB_ENV
 
       - name: Install Cosign