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>

templates/apt/machine-metrics.sh.tpl

@@ -0,0 +1,12 @@
+#!/bin/sh
+# Métriques légères CPU/RAM/disque. Non destructif, rapide, sans installation.
+export LC_ALL=C
+echo "===SU:METRICS_CPU==="
+cat /proc/loadavg 2>/dev/null
+nproc 2>/dev/null
+echo "===SU:METRICS_MEM==="
+grep -E '^(MemTotal|MemAvailable):' /proc/meminfo 2>/dev/null
+echo "===SU:METRICS_FS==="
+df -B1 -T -x tmpfs -x devtmpfs -x overlay -x squashfs 2>/dev/null \
+  | awk 'NR>1 {print "FS\t"$7"\t"$2"\t"$3"\t"$4"\t"$6}'
+echo "===SU:EXIT=0==="