Add master automation on/off switch to Settings

A single global toggle that overrides every zone's own auto_mode —
lets staff pause all HVAC automation stack-wide (e.g. during
maintenance) without touching each zone individually. Backed by the
existing config key/value store; pollOnce() short-circuits entirely
when off (no NewBook fetch, no state tracking, no device commands).

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

backend/src/db.js

@@ -146,6 +146,7 @@ export async function initDb() {
 
 async function seedDefaults() {
   const defaults = {
+    automation_enabled:     true,   // master kill switch — overrides every zone's own auto_mode
     excluded_site_ids:      [],
     poll_interval_minutes:  10,     // matches the old integration's DEFAULT_SCAN_INTERVAL
     default_arrival_time:   '15:00:00',

backend/src/lib/scheduler.js

@@ -148,6 +148,12 @@ async function saveZoneState(zoneId, roomState, bookingStatus) {
 // One poll cycle: fetch bookings once, walk every active room zone, apply heating
 // logic only where the room's state has actually changed since the last cycle.
 export async function pollOnce() {
+  // Master kill switch — overrides every zone's own auto_mode. Off means a full
+  // pause: no NewBook fetch, no state tracking, no device commands. Deliberately
+  // silent (no activity_log entry) since "paused" is a normal standing state, not
+  // an event — the Settings toggle itself is the record of when it changed.
+  if (!(await getConfig('automation_enabled', true))) return
+
   const defaults = {
     default_arrival_time: await getConfig('default_arrival_time', '15:00:00'),
     default_departure_time: await getConfig('default_departure_time', '10:00:00'),

frontend/src/pages/Settings.tsx

@@ -15,6 +15,8 @@ export default function Settings() {
   const [syncing, setSyncing] = useState(false)
 
   const [config, setConfig] = useState<AppConfig | null>(null)
+  const [automationEnabled, setAutomationEnabled] = useState(true)
+  const [automationSaving, setAutomationSaving] = useState(false)
   const [pollMinutes, setPollMinutes] = useState(10)
   const [defaultArrival, setDefaultArrival] = useState('15:00:00')
   const [defaultDeparture, setDefaultDeparture] = useState('10:00:00')
@@ -39,6 +41,7 @@ export default function Settings() {
     loadSites()
     fetchConfig().then(cfg => {
       setConfig(cfg)
+      setAutomationEnabled(cfg.automation_enabled ?? true)
       setPollMinutes(cfg.poll_interval_minutes ?? 10)
       setDefaultArrival(cfg.default_arrival_time ?? '15:00:00')
       setDefaultDeparture(cfg.default_departure_time ?? '10:00:00')
@@ -86,6 +89,21 @@ export default function Settings() {
     }
   }
 
+  async function handleAutomationToggle() {
+    const next = !automationEnabled
+    setAutomationSaving(true); setError(''); setMsg('')
+    try {
+      await updateConfig('automation_enabled', next)
+      setAutomationEnabled(next)
+      setMsg(next ? 'Automation resumed' : 'Automation paused — no setpoints will be sent to any device until resumed')
+      setTimeout(() => setMsg(''), 4000)
+    } catch (e) {
+      setError(e instanceof Error ? e.message : 'Failed to update automation state')
+    } finally {
+      setAutomationSaving(false)
+    }
+  }
+
   async function saveGeneralConfig() {
     setConfigSaving(true); setError(''); setMsg('')
     try {
@@ -130,6 +148,26 @@ export default function Settings() {
       {error && <div className="error-banner">{error}</div>}
       {msg && <div className="ok-banner">{msg}</div>}
 
+      <div className="section-title">Automation</div>
+      <div className="card" style={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between', gap: 16, marginBottom: 24 }}>
+        <div>
+          <div style={{ fontWeight: 600, color: automationEnabled ? 'var(--health-healthy)' : 'var(--danger)' }}>
+            {automationEnabled ? 'Automation is ON' : 'Automation is PAUSED'}
+          </div>
+          <div className="muted" style={{ fontSize: 13, marginTop: 2 }}>
+            Master switch for every zone — overrides each zone's own auto mode. While paused, the scheduler
+            skips its poll entirely: no NewBook fetch, no state tracking, no setpoints sent to any device.
+          </div>
+        </div>
+        <button
+          className={`btn ${automationEnabled ? '' : 'btn-primary'}`}
+          disabled={automationSaving}
+          onClick={handleAutomationToggle}
+        >
+          {automationSaving ? 'Saving…' : automationEnabled ? 'Pause Automation' : 'Resume Automation'}
+        </button>
+      </div>
+
       <div className="section-title">MQTT Broker</div>
       <div className="card" style={{ display: 'flex', alignItems: 'center', gap: 8 }}>
         {mqttConnected ? <Wifi size={16} strokeWidth={1.75} color="var(--health-healthy)" /> : <WifiOff size={16} strokeWidth={1.75} color="var(--danger)" />}

frontend/src/types.ts

@@ -170,6 +170,7 @@ export interface NewbookSite {
 }
 
 export interface AppConfig {
+  automation_enabled?: boolean
   poll_interval_minutes: number
   default_arrival_time: string
   default_departure_time: string