Publish helm chart to separate repo

[TheTechromancer]

Summary

Move the helm chart to its own Docker Hub repo (blacklanternsecurity/bbot-server-helm) to stop the docker image push from clobbering the helm chart manifest at shared bare-semver tags.

Why

The helm-publish and docker-publish jobs both push to blacklanternsecurity/bbot-server. After 0e05b6a dropped the v-prefix from docker tags, the docker push overwrote the helm chart at e.g. 0.1.5 and 0.1.6, so helm pull ... --version 0.1.6 now fails with:

could not load config with mediatype application/vnd.cncf.helm.config.v1+json

Helm derives the OCI repo path from the chart's name:, so renaming the chart to bbot-server-helm routes future pushes to a separate repo. No more shared namespace, no more v-prefix dance.

Changes

• helm/Chart.yaml: name: bbot-server → name: bbot-server-helm
• .github/workflows/docker-tests.yml: helm push bbot-server-*.tgz → bbot-server-helm-*.tgz (matches new packaged filename)
• README.md: update helm install/upgrade commands to use the new chart name
• Docker image repo, PyPI package, GitHub repo, bbctl CLI, and app: bbot-server k8s labels are unchanged

Post-deploy verification

Run after 0.3.0 publishes on stable:

helm pull oci://registry-1.docker.io/blacklanternsecurity/bbot-server-helm --version 0.3.0
docker pull blacklanternsecurity/bbot-server:0.3.0
curl -s "https://hub.docker.com/v2/repositories/blacklanternsecurity/bbot-server/tags/?page_size=10" \
  | jq -r '.results[] | "\(.name)\t\(.media_type)"'
# every tag on the old repo should be application/vnd.oci.image.index.v1+json — no helm mediatypes