fix(ci): create Docker Hub repository before pushing image

The release workflow's Docker push step fails with "denied: requested
access to the resource is denied" because the Docker Hub repository
runtimeverificationinc/komet-node does not yet exist. Docker Hub
requires explicit repository creation before the first push.

This adds a Docker Hub API call to create the repository if it doesn't
already exist, with proper error handling and status reporting.

Author: Copilot

.github/workflows/release.yml

@@ -113,8 +113,39 @@ jobs:
         run: docker run --rm ${TAG} komet-node --help
 
       - name: 'Push Docker image to Docker Hub'
+        env:
+          DOCKERHUB_USERNAME: rvdockerhub
+          DOCKERHUB_PASSWORD: ${{ secrets.DOCKERHUB_PASSWORD }}
+          DOCKERHUB_NAMESPACE: runtimeverificationinc
+          DOCKERHUB_REPO: komet-node
         run: |
-          echo "${{ secrets.DOCKERHUB_PASSWORD }}" | docker login --username rvdockerhub --password-stdin
+          # Log in to Docker Hub
+          echo "${DOCKERHUB_PASSWORD}" | docker login --username "${DOCKERHUB_USERNAME}" --password-stdin
+
+          # Ensure the Docker Hub repository exists (create if missing).
+          # Obtain a Docker Hub JWT for API access.
+          TOKEN=$(curl -s -H "Content-Type: application/json" \
+            -X POST -d "{\"username\":\"${DOCKERHUB_USERNAME}\",\"password\":\"${DOCKERHUB_PASSWORD}\"}" \
+            https://hub.docker.com/v2/users/login/ | jq -r '.token // empty')
+          if [ -z "${TOKEN}" ]; then
+            echo "::warning::Failed to obtain Docker Hub API token; skipping repo creation"
+          else
+            HTTP_CODE=$(curl -s -o /tmp/dockerhub-response.json -w "%{http_code}" \
+              -H "Authorization: JWT ${TOKEN}" \
+              -H "Content-Type: application/json" \
+              -X POST \
+              -d "{\"namespace\":\"${DOCKERHUB_NAMESPACE}\",\"name\":\"${DOCKERHUB_REPO}\",\"is_private\":false,\"description\":\"Komet Node — local Stellar testnet backed by K semantics\"}" \
+              "https://hub.docker.com/v2/repositories/")
+            if [ "${HTTP_CODE}" = "201" ]; then
+              echo "Docker Hub repository created successfully"
+            elif [ "${HTTP_CODE}" = "409" ]; then
+              echo "Docker Hub repository already exists"
+            else
+              echo "::warning::Docker Hub repo creation returned HTTP ${HTTP_CODE}: $(cat /tmp/dockerhub-response.json)"
+            fi
+          fi
+
+          # Push the image
           docker image push ${TAG}
 
       - name: 'On failure, delete drafted release'