Add Daikin local-API driver — MAC-matched subnet sweep instead of UDP broadcast

Daikin BRP069/BRP072-class units are WiFi/DHCP with no fixed IP. hvac's backend
runs as a Docker container on its own bridge network (not directly on the LXC's
admin-VLAN NIC), so UDP broadcast discovery risked silently failing to egress —
instead, every unit is identified by MAC (external_ref), and a background poller
periodically HTTP-sweeps the configured subnet CIDR and matches replies by MAC,
self-healing zone_devices.device_ip whenever a lease changes. Only needs plain
outbound HTTP, same path already proven by the MHI Modbus TCP driver.

- lib/drivers/daikin.js: discover()/getStatus()/setTarget() against the local
  /common/basic_info + /aircon/get_control_info + /aircon/set_control_info API
  (confirmed live against firmware 4_2_303, 2026-08-25). Mode/fan-rate encoding
  taken from community reverse-engineering, not yet verified against a live
  setTarget() call — flagged in comments for first real control test.
- lib/daikin-poller.js: 60s status poll (cached IP) + 5min subnet resweep
  (self-heal IP + auto-register new units, never auto-assigned to a zone).
- lib/device-registry.js: shared discover-upsert, extracted so both the manual
  Discover button and the background sweep record device_ip the same way.
- ac-control.js / routes/override.js: daikin-status/daikin-control endpoints
  and commandAcDevice() branch, mirroring the existing MHI control path.
- Settings page: new "Daikin subnet (CIDR)" field (daikin_subnet_cidr config
  key) — sweeps do nothing until this is set.
- Frontend: DaikinControlPanel.tsx (on/off/mode/setpoint/fan), wired into
  ZoneDetailModal; daikin moved from NOT_YET_IMPLEMENTED to a real driver.

Backend node --check and frontend tsc --noEmit both clean.

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

backend/src/routes/override.js

@@ -94,4 +94,50 @@ export async function overrideRoutes(app) {
 
     return { ok }
   })
+
+  // GET /api/devices/:id/daikin-status — served from the poll-populated cache
+  // (lib/daikin-poller.js), same "read the row, don't do a live round trip" shape as
+  // the mhi_mqtt branch above — Daikin has no push mechanism either, but a live HTTP
+  // call on every panel open would be slower and the cache is at most POLL_MS stale.
+  app.get('/api/devices/:id/daikin-status', { preHandler: requireCap('view') }, async (req, reply) => {
+    const { rows } = await pool.query(
+      `SELECT * FROM zone_devices WHERE id = $1 AND device_type = 'daikin'`,
+      [req.params.id]
+    )
+    if (!rows.length) return reply.status(404).send({ error: 'Daikin device not found' })
+    const device = rows[0]
+
+    return {
+      external_ref: device.external_ref,
+      onOff: device.power_state ?? undefined,
+      mode: device.current_mode ?? undefined,
+      setpoint: device.current_target_temp != null ? Number(device.current_target_temp) : undefined,
+      fanSpeed: device.fan_speed ?? undefined,
+      roomTemp: device.current_room_temp != null ? Number(device.current_room_temp) : undefined,
+      status_updated_at: device.status_updated_at,
+    }
+  })
+
+  // POST /api/devices/:id/daikin-control — explicit staff control from DaikinControlPanel.
+  // Body: { onOff?, mode?, tempC?, fanSpeed? }. Shares commandAcDevice() with the mhi
+  // routes above and with the scheduler's automatic occupied/vacant AC control.
+  app.post('/api/devices/:id/daikin-control', { preHandler: requireCap('control') }, async (req, reply) => {
+    const { rows } = await pool.query(
+      `SELECT * FROM zone_devices WHERE id = $1 AND device_type = 'daikin'`,
+      [req.params.id]
+    )
+    if (!rows.length) return reply.status(404).send({ error: 'Daikin device not found' })
+    const device = rows[0]
+    const { onOff, mode, tempC, fanSpeed } = req.body || {}
+
+    const { ok } = await commandAcDevice(device, { onOff, mode, tempC, fanSpeed }, { origin: 'manual', log: req.log })
+
+    await logActivity(device.zone_id, 'device_command', {
+      note: `Daikin manual control on ${device.location || device.discovered_name || device.external_ref}: ${JSON.stringify({ onOff, mode, tempC, fanSpeed })}${ok ? '' : ' — FAILED'}`,
+      source: 'manual',
+      userEmail: req.user.email,
+    })
+
+    return { ok }
+  })
 }