Add MHI aircon manual control (Phase 2, Modbus only)

Manual on/off/mode/setpoint/fan control for MHI indoor units via the
already-verified Intesis Modbus TCP gateway, deliberately NOT wired into
the NewBook-driven scheduler yet — that stays deferred. Modbus doesn't
depend on the MQTT broker (separate infra, still unbuilt), so this can be
deployed and tested standalone.

- mhi_gateways table (connection config: host/port/slave id/address base)
  + zone_devices columns for MHI devices (gateway id, unit index, IU hint,
  and the per-device register map staged from a MAPS import — ground
  truth, never re-derived from room/IU at runtime)
- drivers/mhi-modbus.js: discover/getStatus/setTarget over modbus-serial,
  same interface as trv.js/homeassistant.js; per-gateway request queue
  since Modbus TCP requires serialised requests; falls back to the
  profile's stride formula (with a loud warning) only if a unit has never
  been through an import
- routes/mhi-gateways.js: gateway CRUD, live test-connection, xlsx import
  (stages the parsed result for review — never auto-creates devices),
  per-unit 'assign to zone' as the explicit commit step
- routes/override.js: GET .../mhi-status, POST .../mhi-control (control cap)
- frontend: GatewaysPanel (add gateway, test connection, import + preview,
  assign units) and MhiControlPanel (on/off, mode, setpoint, fan) wired
  into Devices.tsx / ZoneDetailModal.tsx

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

backend/src/routes/mhi-gateways.js

@@ -0,0 +1,149 @@
+import { requireAuth, requireCap } from '../auth.js'
+import { pool } from '../db.js'
+import { parseIntesisMapsExport } from '../lib/mhi-xlsx-import.js'
+import * as mhiDriver from '../lib/drivers/mhi-modbus.js'
+
+// MHI Modbus TCP gateway configuration + register-map import. Manual control
+// only for now (see lib/drivers/mhi-modbus.js) — this never touches
+// lib/scheduler.js. Importing a MAPS export only STAGES the parsed result on
+// the gateway row for staff review; no zone_devices rows are created until an
+// explicit "Assign to Zone" per unit (see the /units/:unitIndex/assign route).
+export async function mhiGatewayRoutes(app) {
+  app.addHook('preHandler', requireAuth)
+
+  // GET /api/mhi-gateways — configured gateways + how many units are assigned from each
+  app.get('/api/mhi-gateways', { preHandler: requireCap('view') }, async () => {
+    const { rows } = await pool.query(`
+      SELECT g.*,
+        (SELECT COUNT(*)::int FROM zone_devices zd WHERE zd.mhi_gateway_id = g.id) AS assigned_count
+      FROM mhi_gateways g
+      ORDER BY g.name
+    `)
+    return rows
+  })
+
+  // POST /api/mhi-gateways — { name, host, port, slaveId, addressBase }
+  app.post('/api/mhi-gateways', { preHandler: requireCap('manage_devices') }, async (req, reply) => {
+    const { name, host, port, slaveId, addressBase } = req.body || {}
+    if (!name || !host) return reply.status(400).send({ error: 'name and host are required' })
+
+    const { rows } = await pool.query(
+      `INSERT INTO mhi_gateways (name, host, port, slave_id, address_base)
+       VALUES ($1, $2, $3, $4, $5) RETURNING *`,
+      [name, host, port || 502, slaveId || 1, addressBase ?? 0]
+    )
+    return rows[0]
+  })
+
+  // PATCH /api/mhi-gateways/:id — edit connection details
+  app.patch('/api/mhi-gateways/:id', { preHandler: requireCap('manage_devices') }, async (req, reply) => {
+    const { rows: existing } = await pool.query('SELECT * FROM mhi_gateways WHERE id = $1', [req.params.id])
+    if (!existing.length) return reply.status(404).send({ error: 'Gateway not found' })
+    const g = existing[0]
+    const { name, host, port, slaveId, addressBase } = req.body || {}
+
+    const { rows } = await pool.query(
+      `UPDATE mhi_gateways SET
+         name = $1, host = $2, port = $3, slave_id = $4, address_base = $5, updated_at = NOW()
+       WHERE id = $6 RETURNING *`,
+      [
+        name ?? g.name, host ?? g.host, port ?? g.port,
+        slaveId ?? g.slave_id, addressBase ?? g.address_base, req.params.id,
+      ]
+    )
+    return rows[0]
+  })
+
+  // POST /api/mhi-gateways/:id/test-connection — live Modbus read of the
+  // gateway comm status register (same check as scripts/test-modbus-connection.py)
+  app.post('/api/mhi-gateways/:id/test-connection', { preHandler: requireCap('manage_devices') }, async (req, reply) => {
+    const { rows } = await pool.query('SELECT * FROM mhi_gateways WHERE id = $1', [req.params.id])
+    if (!rows.length) return reply.status(404).send({ error: 'Gateway not found' })
+    const result = await mhiDriver.discover(rows[0])
+    return result
+  })
+
+  // POST /api/mhi-gateways/:id/import — multipart .xlsx upload (same
+  // @fastify/multipart pattern as devices.js's photo upload route). Parses and
+  // STAGES the result on the gateway row — nothing else is written.
+  app.post('/api/mhi-gateways/:id/import', { preHandler: requireCap('manage_devices') }, async (req, reply) => {
+    const { rows: existing } = await pool.query('SELECT id FROM mhi_gateways WHERE id = $1', [req.params.id])
+    if (!existing.length) return reply.status(404).send({ error: 'Gateway not found' })
+
+    let fileBuffer = null, fileName = null
+    for await (const part of req.parts()) {
+      if (part.type === 'file') {
+        const chunks = []
+        for await (const chunk of part.file) chunks.push(chunk)
+        fileBuffer = Buffer.concat(chunks)
+        fileName = part.filename
+      }
+    }
+    if (!fileBuffer) return reply.status(400).send({ error: 'No file uploaded' })
+
+    let parsed
+    try {
+      parsed = parseIntesisMapsExport(fileBuffer)
+    } catch (err) {
+      return reply.status(400).send({ error: err.message })
+    }
+
+    const { rows } = await pool.query(
+      `UPDATE mhi_gateways SET imported_filename = $1, imported_units = $2, imported_at = NOW(), updated_at = NOW()
+       WHERE id = $3 RETURNING *`,
+      [fileName, JSON.stringify(parsed), req.params.id]
+    )
+    return rows[0]
+  })
+
+  // POST /api/mhi-gateways/:id/units/:unitIndex/assign — { zone_id, location }
+  // creates/updates a zone_devices row (device_type='mhi_modbus') from the
+  // gateway's last staged import. Pulls that unit's `fields` register map
+  // straight from imported_units — this is the one-time "commit" step for a
+  // unit; re-running an import + re-assigning refreshes the stored map.
+  app.post('/api/mhi-gateways/:id/units/:unitIndex/assign', { preHandler: requireCap('manage_devices') }, async (req, reply) => {
+    const { rows: gwRows } = await pool.query('SELECT * FROM mhi_gateways WHERE id = $1', [req.params.id])
+    if (!gwRows.length) return reply.status(404).send({ error: 'Gateway not found' })
+    const gateway = gwRows[0]
+
+    const unitIndex = parseInt(req.params.unitIndex, 10)
+    if (!Number.isFinite(unitIndex)) return reply.status(400).send({ error: 'Invalid unit index' })
+
+    const unit = (gateway.imported_units?.units || []).find(u => u.unitIndex === unitIndex)
+    if (!unit) {
+      return reply.status(404).send({
+        error: `Unit ${unitIndex} not found in this gateway's last import — import (or re-import) the MAPS export first.`,
+      })
+    }
+
+    const { zone_id, location } = req.body || {}
+    const externalRef = `mhi:${gateway.id}:${unitIndex}`
+
+    const { rows } = await pool.query(
+      `INSERT INTO zone_devices
+         (device_type, external_ref, discovered_name, zone_id, location,
+          mhi_gateway_id, mhi_unit_index, mhi_iu_address, mhi_register_map)
+       VALUES ('mhi_modbus', $1, $2, $3, $4, $5, $6, $7, $8)
+       ON CONFLICT (device_type, external_ref) DO UPDATE SET
+         zone_id           = EXCLUDED.zone_id,
+         location          = EXCLUDED.location,
+         mhi_gateway_id    = EXCLUDED.mhi_gateway_id,
+         mhi_unit_index    = EXCLUDED.mhi_unit_index,
+         mhi_iu_address    = EXCLUDED.mhi_iu_address,
+         mhi_register_map  = EXCLUDED.mhi_register_map,
+         updated_at        = NOW()
+       RETURNING *`,
+      [
+        externalRef,
+        `MHI Unit ${unitIndex}`,
+        zone_id || null,
+        location || null,
+        gateway.id,
+        unitIndex,
+        unit.iu ?? null,
+        JSON.stringify(unit.fields),
+      ]
+    )
+    return rows[0]
+  })
+}