swarmexec v1.3.0 — Networks and Secrets in the interactive UI

Two new read-only tabs in `swarmexec ui`:
- Networks (4): driver, scope, type, and the services/containers attached
  to each network (containers nested under their service).
- Secrets (5): metadata, a used-by count, and the services/containers that
  reference each secret. Secret values are never shown — the Docker API
  does not expose them.

Also in this release: per-service health in the container tree
(running/desired count + health color), fold markers (▸/▾) with working
h/l folding, and a site analytics + privacy page.