fix: disable provenance in docker build to fix GitLab Registry 0B display

Add `--provenance=false` flag to `docker build` command. This stops Docker BuildKit
from generating OCI Referrers/attestations, which are not correctly parsed by GitLab
Container Registry and cause the UI to display 0B size and "missing manifest digest" errors.

.gitlab-ci.yml

@@ -35,6 +35,7 @@ package:
     - JAR_FILE=$(find build/libs -name '*.jar' | head -1)
     - echo "Building Docker image for tag $CI_COMMIT_TAG with JAR $JAR_FILE"
     - docker build
+        --provenance=false
         -f Dockerfile.ci
         --build-arg JAR_FILE="$JAR_FILE"
         -t "$CI_REGISTRY_IMAGE:$CI_COMMIT_TAG"