Dispatch api-release to both services after a release publishes #90

Goal

Each api release tells service-api-standard and service-api-chain which version just shipped. Decided in #79.

Acceptance criteria

• release.yml gains a final job, needs: [github-release], so it runs only after the release has published.
• It mints a token with actions/create-github-app-token, from vars.RELEASE_BOT_APP_ID and secrets.RELEASE_BOT_PRIVATE_KEY, scoped to the two services.
• It sends repository_dispatch with event_type: api-release and client_payload.version set to the tag (e.g. v0.8.0) to both services.
• A failed dispatch fails the job visibly. The module and npm package are already published by then, so re-running this job alone is the recovery; that's noted in a comment beside it.

Verification

After the next api release, the Release run shows the dispatch job green, and both services' Actions tabs show a bump-api run triggered by repository_dispatch for that version.

Depends on

#89, the release-bot GitHub App.