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>

renderer/index.html

@@ -13,7 +13,7 @@
     <div class="brand">PON Fleet Upgrader</div>
     <nav id="tabs" class="tabs hidden">
       <button class="tab" data-tab="dashboard" data-view="#view-dashboard">Dashboard</button>
-      <button class="tab" data-tab="onu" data-view="#view-fleet">ONU</button>
+      <button class="tab" data-tab="onu" data-view="#view-onu-info">ONU</button>
       <button class="tab" data-tab="olt" data-view="#view-olts">OLT</button>
     </nav>
     <div class="session" id="session-label">Not connected</div>
@@ -66,9 +66,47 @@
     </div>
   </section>
 
+  <!-- ================= ONU info / stats view ================= -->
+  <section id="view-onu-info" class="view hidden">
+    <div class="panel-left">
+      <nav class="subtabs">
+        <button class="subtab" data-subview="#view-onu-info">Info / stats</button>
+        <button class="subtab" data-subview="#view-fleet">Fleet &amp; upgrade</button>
+      </nav>
+      <h2>Find ONU</h2>
+      <label>Search (name / address / serial)
+        <input id="onu-info-search" type="search" placeholder="e.g. ORKANGER or GNXS05…" />
+      </label>
+      <label>Registration status
+        <select id="onu-info-status">
+          <option value="">Any</option>
+          <option value="__down__">Down (Dereg / Dying Gasp / Disabled)</option>
+          <option value="Registered">Registered</option>
+          <option value="Deregistered">Deregistered</option>
+          <option value="Dying Gasp">Dying Gasp</option>
+          <option value="Disabled">Disabled</option>
+          <option value="__unknown__">Unknown (no OLT state)</option>
+        </select>
+      </label>
+      <button id="onu-info-load" class="primary">Load fleet</button>
+      <p class="muted small" id="onu-info-status-line">Load the fleet, then pick an ONU.</p>
+      <div class="onu-info-list" id="onu-info-list"></div>
+    </div>
+
+    <div class="panel-main">
+      <div id="onu-info-detail" class="onu-detail">
+        <p class="muted">Select an ONU on the left to see its stats and the CPE (customer router) behind it.</p>
+      </div>
+    </div>
+  </section>
+
   <!-- ================= Fleet view ================= -->
   <section id="view-fleet" class="view hidden">
     <div class="panel-left">
+      <nav class="subtabs">
+        <button class="subtab" data-subview="#view-onu-info">Info / stats</button>
+        <button class="subtab" data-subview="#view-fleet">Fleet &amp; upgrade</button>
+      </nav>
       <h2>Filters</h2>
       <label>Name / address contains
         <input id="filter-text" type="search" placeholder="e.g. ORKANGER" />