Phase 17: multi-host dashboard (0.19.0)

The dashboard now renders a stacks-with-usage table per host: the local host
plus a section for each registered agent (online dot + offline notice), reusing
the same CPU/memory meters and inline start/stop/restart actions.

- agent_app.py: GET /agent/stacks/stats (reuses stats_service); /agent/system
  now also returns cpu_cores + mem_total for remote meter references.
- routers/agents.py: proxy GET /api/agents/{id}/stacks/stats (declared before
  /{agent_id}/stacks/{stack_id}).
- Frontend: agentsApi.system + stackStats; Dashboard refactored into a shared
  StacksTable used by the local section and a per-agent AgentDashboardSection.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -9,7 +9,8 @@ as intuitive as Dockge, as capable as Portainer for Compose workflows.
 > + Phase 9 (Networks) + Phase 10 (iGPU passthrough) + Phase 11 (Remote UX &
 > network attach) + Phase 12 (File browser) + Phase 13 (Multi-host networks &
 > images) + Phase 14 (Multi-host file browser) + Phase 15 (Dashboard stack
-> resource usage) + Phase 16 (Volumes page, multi-host) complete.
+> resource usage) + Phase 16 (Volumes page, multi-host) + Phase 17 (Multi-host
+> dashboard) complete.
 
 ## What works today (Phase 1)
 
@@ -147,6 +148,15 @@ as intuitive as Dockge, as capable as Portainer for Compose workflows.
   container or connect any container on the host (`POST /api/networks/{id}/connect`
   / `/disconnect`).
 
+### Phase 17 — Multi-host dashboard
+
+- The dashboard now shows a **stacks-with-usage table per host** — the local host
+  plus a section for each registered agent (online dot, offline notice), with the
+  same CPU/memory meters and inline start/stop/restart as the local list.
+- New agent endpoint `/agent/stacks/stats` (proxied at
+  `/api/agents/{id}/stacks/stats`); `/agent/system` now also reports `cpu_cores`
+  and `mem_total` so remote meters have a host reference.
+
 ### Phase 16 — Volumes page (multi-host)
 
 - **New Volumes page** (sidebar) with per-host sections (local + each online