[Bug]: Empty setup.kibana in Beats configs makes dashboard loading default to localhost

All three Beats templates render an empty setup.kibana: block, so no Kibana endpoint is configured. When a beat loads dashboards (e.g. <beat> setup --dashboards), it falls back to the default localhost:5601 — the wrong host in a full stack.

Resolve setup.kibana.host in two branches:

• full stack: from the Kibana inventory host (groups[...] | first) + elasticstack_kibana_port. Scheme is https when elasticstack_kibana_tls (new shared flag, default false) is set, otherwise http.
• standalone: from a new beats_kibana_host (full URL, e.g. a cloud Kibana), unset by default; when unset, skip setup.kibana entirely.

When the resulting URL is https, render the setup.kibana.ssl block using the shared Beats SSL settings from #513 (verification_mode + CA resolution: stack CA in a full stack, user-provided CA standalone, OS system store for public/cloud CAs).

Only relevant when dashboards are loaded. Related: #503 (Kibana serving https), #513 (shared SSL settings).

Depends on: #513 (shared SSL settings), #503 (Kibana serving https), and #524 (service addressing mode).

Locate the three Beats templates that render the empty setup.kibana block, then inspect the setup.kibana.host entry point and the setup --dashboards flow. Use the requirements from #513, #503, and #524 to determine full-stack and standalone addressing and SSL behavior. Done means dashboards use the resolved endpoint, omit setup.kibana when standalone has no host, and render SSL settings for HTTPS.