Scaffold Phase 1 hvac app — NewBook-driven room TRV heating scheduler

Ports the state machine, retry/backoff, and guest-override detection from
the retired homeassistant-newbook-heating-component, without depending on
Home Assistant. Backend (Fastify/pg) + frontend (React/Vite/TS) following
standard stack conventions; LXC 128 (127 was already taken by utilities).

MHI/Midea/Daikin/boiler drivers and the shared MQTT broker (LXC 104) are
later phases/infra, not included here.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/components/ZoneCard.tsx

@@ -0,0 +1,27 @@
+import { Thermometer, BatteryLow } from 'lucide-react'
+import type { ZoneStatus } from '../types'
+import { ROOM_STATE_LABELS } from '../types'
+
+export default function ZoneCard({ zone, onClick }: { zone: ZoneStatus; onClick: () => void }) {
+  const unhealthy = zone.devices.filter(d => d.health_state !== 'healthy').length
+  const lowBattery = zone.devices.some(d => d.battery_pct != null && d.battery_pct < 30)
+
+  return (
+    <div className={`card zone-card st-${zone.room_state}`} onClick={onClick}>
+      <div className="zone-card-title">
+        <span>{zone.name}</span>
+        {!zone.auto_mode && <span className="badge badge-outline">Manual</span>}
+      </div>
+      <div className={`badge badge-st-${zone.room_state}`}>{ROOM_STATE_LABELS[zone.room_state]}</div>
+      <div className="zone-card-temp">
+        <Thermometer size={16} strokeWidth={1.75} style={{ verticalAlign: '-2px', marginRight: 4 }} />
+        {Number(zone.target_temp).toFixed(1)}°C
+      </div>
+      <div className="zone-card-meta">
+        <span>{zone.device_count ?? zone.devices.length} device{(zone.device_count ?? zone.devices.length) === 1 ? '' : 's'}</span>
+        {unhealthy > 0 && <span style={{ color: 'var(--health-degraded)' }}>{unhealthy} needs attention</span>}
+        {lowBattery && <BatteryLow size={13} strokeWidth={1.75} color="var(--health-degraded)" />}
+      </div>
+    </div>
+  )
+}