onu: info/stats sub-tab with CPE lease health + OUI vendor

Adds an ONU info page and splits the ONU tab into two sub-tabs (Info / stats,
Fleet & upgrade). The ONU tab now lands on Info; campaign/verify keep the
Fleet sub-tab lit.

ONU info page (#view-onu-info): master-detail over the already-loaded fleet
(search + status filter, no new bulk fetch). Per-ONU detail shows identity,
link/optical + FEC (read from the merged ONU-STATE), firmware, and a CPE card.

CPE (customer router):
- McmsClient.getCpe — GET /api/cpe/onu/<id>/ (unversioned, [status,doc] tuple).
- src/cpe.js (pure, shared): summarizeCpe + leaseHealth. Renewal rule —
  <50% of the lease remaining => "renewal overdue" (amber), past end =>
  expired. v4 expiry = DHCP "Remove Time"; v6 spans Last Success ->
  Preferred Lifetime (T1 midpoint), with Prefix Delegation surfaced.
- api:getOnuCpe (main.js + web/server.js, exposed in both bridges).

OUI vendor (src/oui.js, pure, shared): lazy fetch of the IEEE oui.csv,
prefix->org map, cached in memory ~30 days + best-effort to disk
(PFW_CACHE_DIR / temp; PrivateTmp makes /tmp writable). Resolved server-side
in getOnuCpe; every failure degrades to "unknown OUI". CPE itself is not
TTL-cached (lease must be live); only the OUI list is.

Dashboard abnormal Rx/Tx rows are now clickable -> deep-link to that ONU's
info page (showListModal gained per-item onClick).

Docs: CLAUDE.md §17 + IPC table + intro; README.

Verified: node --check; cpe.js/oui.js unit-tested (15/15: lease ok/warn/
expired/unknown + 50% boundary, v6 prefix parse, OUI quoted-CSV parse +
lookup); ONU info page + CPE card rendered offscreen over HTTP.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

main.js

@@ -13,6 +13,8 @@ const {
   summarizeOltNniNetworks, planNniEdit,
 } = require('./src/mcms-api');
 const { summarizeDashboard } = require('./src/dashboard');
+const { summarizeCpe } = require('./src/cpe');
+const { lookupOui } = require('./src/oui');
 const { planUpgrade, activeBankPtr, inactiveBank } = require('./src/bank-strategy');
 
 /** @type {McmsClient | null} */
@@ -219,6 +221,23 @@ ipcMain.handle('api:getOnuConfig', async (_ev, { onuId }) => {
   }
 });
 
+/**
+ * CPE (customer router) behind an ONU, for the ONU info page: DHCPv4/v6
+ * lease state + renewal health, plus the CPE MAC's vendor (OUI lookup,
+ * cached ~1 month). Returns null when there's no CPE record.
+ */
+ipcMain.handle('api:getOnuCpe', async (_ev, { onuId }) => {
+  try {
+    const c = requireClient();
+    const doc = await c.getCpe(onuId);
+    const cpe = summarizeCpe(doc);
+    if (cpe) cpe.cpeVendor = await lookupOui(cpe.cpeMac);
+    return { ok: true, data: cpe };
+  } catch (err) {
+    return { ok: false, error: toWireError(err) };
+  }
+});
+
 ipcMain.handle('api:listOnuFirmware', async () => {
   try {
     const c = requireClient();