feat(docker): uptime from StartedAt, a restart is an event, host totals count physical devices only (#5153)

- Agent: started_at comes from inspect's State.StartedAt (nanoseconds
  trimmed; Docker's zero time is "never started"), not the list's Created,
  so a restarted container's uptime counts from its restart.
- A rising restart_count between two snapshots emits a "restart" event
  ("restart #3", or "3 restarts, now #5"), said instead of a start; a
  restart then a death gives both. A count that falls (recreated under the
  same name) says nothing. The timeline draws it as ↻.
- Network and disk I/O count what the kernel calls physical: interfaces
  not under /sys/devices/virtual/net (bridges, docker0, veth, vxlan, tun),
  block devices with a device behind them (not dm, md, zram), so a byte is
  not counted twice. Where /sys calls everything virtual (an agent in LXC)
  the name-filtered set is kept rather than reporting no traffic.
- Agent tests updated for #5152's (status, detail, containers) and
  (is_manager, topology) shapes; the no-Docker disk test now states the
  case it was passing for by accident.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugins/docker/routes.py

@@ -303,6 +303,7 @@ async def host_panel(host_id: str):
 # Glyph + colour per lifecycle event, so the timeline reads at a glance.
 _EVENT_STYLE = {
     "start":         ("▲", "var(--green)"),
+    "restart":       ("↻", "var(--yellow)"),
     "stop":          ("■", "var(--text-muted)"),
     "die":           ("✕", "var(--red)"),
     "oom":           ("☠", "var(--red)"),