feat(metrics): machine_metrics_simple — CPU/RAM/disque live par machine (tâche 4)

- template machine-metrics (loadavg/nproc, /proc/meminfo, df -B1) non destructif
- parseMetrics (TDD) → cpu load/cores, mémoire kB→B + %, filesystems, warnings >=90%
- collectMetrics (SSH léger) persiste machine_metrics_latest ; getLatestMetrics (sans SSH)
- routes GET /machines/:id/metrics + POST /metrics/collect ; api latestMetrics/collectMetrics
- section Hardware : bloc métriques live (CPU/RAM/disques + alertes) + bouton Collecter
  → comble le gap « Health » de la tâche 3

tsc 0 · 108 tests · build OK.

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

server/routes/machines.ts

@@ -7,6 +7,7 @@ import {
 } from "../services/machines.js";
 import { refreshMachine, getLatestSnapshot } from "../services/refresh.js";
 import { runProbe } from "../services/machineProbe.js";
+import { collectMetrics, getLatestMetrics } from "../services/machineMetrics.js";
 
 export const machinesRoutes = new Hono();
 
@@ -54,6 +55,18 @@ machinesRoutes.patch("/:id", async (c) => {
   }
 });
 
+// Dernières métriques stockées (sans SSH).
+machinesRoutes.get("/:id/metrics", (c) => c.json(getLatestMetrics(c.req.param("id"))));
+
+// Collecte fraîche (SSH léger, non destructif).
+machinesRoutes.post("/:id/metrics/collect", async (c) => {
+  try {
+    return c.json(await collectMetrics(c.req.param("id")));
+  } catch (err) {
+    return c.json({ error: (err as Error).message }, 400);
+  }
+});
+
 machinesRoutes.get("/:id/hardware", (c) => {
   try {
     return c.json(getMachineHardware(c.req.param("id")));