Dashboard: rebuild into an operator cockpit (0.38.0)

Replace the analytics-style dashboard (stack-health funnel, uptime %,
operations/day grid, AI pill) with an attention-driven fleet cockpit:

- New /api/dashboard/fleet endpoint: server-side fan-out across the local
  host and every agent into one payload — a prioritized "needs attention"
  list, headline KPIs, an honest stack-status breakdown and a per-host
  resource rollup. Each agent uses its own DB session so the fan-out is
  concurrency-safe; failures degrade to "offline" instead of stalling.
- New frontend: AttentionStrip, FleetKpiRow, StackStatusBar and
  HostResourceTable; Dashboard.tsx rewritten around them.
- Remove the funnel/summary endpoints, the uptime sampler loop and the
  ops-activity machinery; delete the now-unused chart components.

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

frontend/src/components/dashboard/HostResourceTable.tsx

@@ -0,0 +1,100 @@
+import { Link } from "react-router-dom";
+import type { FleetHost } from "@/api/dashboard";
+import { cn, formatBytes } from "@/lib/utils";
+
+const DISK_PRESSURE = 85;
+const MEM_PRESSURE = 90;
+
+function Meter({ used, total, pressure }: { used: number; total: number; pressure: number }) {
+  const pct = total > 0 ? Math.round((used / total) * 100) : 0;
+  const hot = pct >= pressure;
+  return (
+    <div className="min-w-[7rem]">
+      <div className="mb-1 flex items-center justify-between text-xs">
+        <span className={cn("font-semibold", hot ? "text-red-600 dark:text-red-400" : "text-sp-text-1")}>
+          {pct}%
+        </span>
+        <span className="text-sp-text-3">
+          {formatBytes(used)} / {formatBytes(total)}
+        </span>
+      </div>
+      <div className="h-1.5 rounded-pill bg-sp-surface-2">
+        <div
+          className={cn("h-1.5 rounded-pill", hot ? "bg-red-500" : "bg-sp-blue")}
+          style={{ width: `${Math.min(pct, 100)}%` }}
+        />
+      </div>
+    </div>
+  );
+}
+
+export function HostResourceTable({ hosts }: { hosts: FleetHost[] }) {
+  return (
+    <div className="sp-card overflow-hidden p-0">
+      <div className="border-b border-sp-border px-4 py-2.5">
+        <h2 className="sp-label">Hosts</h2>
+      </div>
+      <div className="overflow-x-auto">
+        <table className="w-full text-sm">
+          <thead>
+            <tr className="text-left text-xs text-sp-text-3">
+              <th className="px-4 py-2 font-medium">Host</th>
+              <th className="px-4 py-2 font-medium">CPU</th>
+              <th className="px-4 py-2 font-medium">Memory</th>
+              <th className="px-4 py-2 font-medium">Disk</th>
+              <th className="px-4 py-2 font-medium">Containers</th>
+              <th className="px-4 py-2 font-medium">Stacks</th>
+            </tr>
+          </thead>
+          <tbody className="divide-y divide-sp-border">
+            {hosts.map((h) => (
+              <tr key={String(h.id)} className="align-middle">
+                <td className="px-4 py-3">
+                  <div className="flex items-center gap-2">
+                    <span
+                      className={cn(
+                        "h-2.5 w-2.5 shrink-0 rounded-full",
+                        h.online ? "bg-sp-green" : "bg-slate-400"
+                      )}
+                      title={h.status}
+                    />
+                    <span className="font-medium text-sp-text-1">{h.name}</span>
+                  </div>
+                </td>
+                {h.online ? (
+                  <>
+                    <td className="px-4 py-3 text-sp-text-2">{h.cpu_cores || "—"}</td>
+                    <td className="px-4 py-3">
+                      <Meter used={h.mem_used} total={h.mem_total} pressure={MEM_PRESSURE} />
+                    </td>
+                    <td className="px-4 py-3">
+                      <Meter used={h.disk_used} total={h.disk_total} pressure={DISK_PRESSURE} />
+                    </td>
+                    <td className="px-4 py-3 text-sp-text-2">
+                      {h.containers_running}/{h.containers_total}
+                    </td>
+                    <td className="px-4 py-3 text-sp-text-2">
+                      {h.stacks.running}/{h.stacks.total}
+                      {h.unhealthy > 0 && (
+                        <span className="ml-1.5 text-xs font-semibold text-red-600 dark:text-red-400">
+                          · {h.unhealthy} unhealthy
+                        </span>
+                      )}
+                    </td>
+                  </>
+                ) : (
+                  <td className="px-4 py-3 text-sp-text-3" colSpan={5}>
+                    {h.status} —{" "}
+                    <Link to="/settings" className="text-sp-blue hover:underline">
+                      check under Settings
+                    </Link>
+                  </td>
+                )}
+              </tr>
+            ))}
+          </tbody>
+        </table>
+      </div>
+    </div>
+  );
+}