Replace ad-hoc empty-state markup across Dashboard, TopologyList,
LiveLogs, Attackers, Bounty, AttackerDetail, SwarmHosts, RemoteUpdates
and CommandPalette with the new <EmptyState> component. Themed icons
+ hints improve discoverability; TopologyList and SwarmHosts gain
CTAs to their respective creation flows.
React component for /swarm-updates: per-host table polled every 10s,
row actions for Push Update / Update Updater / Rollback, a fleet-wide
'Push to All' modal with the include_self toggle, and toast feedback
per result.
Admin-only (both server-gated and UI-gated). Unreachable hosts surface
as an explicit state; actions are disabled on them. Rollback is
disabled when the worker has no previous release slot (previous_sha
null from /hosts).
