Dashboard: per-host resource overview bar (0.20.0)

The dashboard resource bar (CPU cores, memory used/total, containers, Docker
version) is now rendered per host instead of once for the local host — each
host section (local + each agent) shows its own bar above its stacks table.

- agent_app.py: _system_info() now also returns mem_used (from meminfo
  available), alongside the cpu_cores/mem_total added in 0.19.0.
- Frontend: extracted a ResourceBar component used by the local section and each
  AgentDashboardSection; AgentSystem type gained mem_used.

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

frontend/src/api/agents.ts

@@ -10,6 +10,7 @@ export interface AgentSystem {
   host_os: string;
   cpu_cores: number;
   mem_total: number;
+  mem_used: number;
   containers_running: number;
   containers_total: number;
 }

frontend/src/pages/Dashboard.tsx

@@ -51,33 +51,21 @@ export function Dashboard() {
         </Link>
       )}
 
-      {/* Local host resource bar */}
-      <div className="grid grid-cols-2 gap-4 md:grid-cols-4">
-        <Stat icon={<Cpu className="h-5 w-5" />} label="CPU cores" value={info.data?.cpu_cores ?? "—"} />
-        <Stat
-          icon={<MemoryStick className="h-5 w-5" />}
-          label="Memory"
-          value={
-            info.data
-              ? `${formatBytes(info.data.ram.used)} / ${formatBytes(info.data.ram.total)}`
-              : "—"
-          }
-        />
-        <Stat
-          icon={<Container className="h-5 w-5" />}
-          label="Containers"
-          value={info.data ? `${info.data.containers_running} / ${info.data.containers_total}` : "—"}
-        />
-        <Stat icon={<HardDrive className="h-5 w-5" />} label="Docker" value={info.data?.docker_version ?? "—"} />
-      </div>
-
-      {/* Local stacks */}
+      {/* Local host */}
       <section>
         {hasAgents ? (
           <HostHeader />
         ) : (
-          <h2 className="mb-3 text-sm font-semibold uppercase tracking-wide text-slate-500">Stacks</h2>
+          <h2 className="mb-3 text-sm font-semibold uppercase tracking-wide text-slate-500">This host</h2>
         )}
+        <ResourceBar
+          cpuCores={info.data?.cpu_cores ?? 0}
+          memUsed={info.data?.ram.used ?? 0}
+          memTotal={info.data?.ram.total ?? 0}
+          containersRunning={info.data?.containers_running ?? 0}
+          containersTotal={info.data?.containers_total ?? 0}
+          dockerVersion={info.data?.docker_version ?? ""}
+        />
         <StacksTable
           stacks={stacks.data}
           stats={stats.data}
@@ -175,6 +163,15 @@ function AgentDashboardSection({ agent, isAdmin }: { agent: Agent; isAdmin: bool
           </p>
         </Card>
       ) : (
+        <>
+        <ResourceBar
+          cpuCores={sys.data?.cpu_cores ?? 0}
+          memUsed={sys.data?.mem_used ?? 0}
+          memTotal={sys.data?.mem_total ?? 0}
+          containersRunning={sys.data?.containers_running ?? 0}
+          containersTotal={sys.data?.containers_total ?? 0}
+          dockerVersion={sys.data?.docker_version ?? ""}
+        />
         <StacksTable
           stacks={stacks.data}
           stats={stats.data}
@@ -189,6 +186,7 @@ function AgentDashboardSection({ agent, isAdmin }: { agent: Agent; isAdmin: bool
           onRestart={(id) => run("restart", "Restarting", id)}
           emptyText="No stacks on this host."
         />
+        </>
       )}
     </section>
   );
@@ -418,6 +416,39 @@ function Meter({
   );
 }
 
+function ResourceBar({
+  cpuCores,
+  memUsed,
+  memTotal,
+  containersRunning,
+  containersTotal,
+  dockerVersion,
+}: {
+  cpuCores: number;
+  memUsed: number;
+  memTotal: number;
+  containersRunning: number;
+  containersTotal: number;
+  dockerVersion: string;
+}) {
+  return (
+    <div className="mb-4 grid grid-cols-2 gap-4 md:grid-cols-4">
+      <Stat icon={<Cpu className="h-5 w-5" />} label="CPU cores" value={cpuCores || "—"} />
+      <Stat
+        icon={<MemoryStick className="h-5 w-5" />}
+        label="Memory"
+        value={memTotal ? `${formatBytes(memUsed)} / ${formatBytes(memTotal)}` : "—"}
+      />
+      <Stat
+        icon={<Container className="h-5 w-5" />}
+        label="Containers"
+        value={`${containersRunning} / ${containersTotal}`}
+      />
+      <Stat icon={<HardDrive className="h-5 w-5" />} label="Docker" value={dockerVersion || "—"} />
+    </div>
+  );
+}
+
 function Stat({
   icon,
   label,