Admin customer detail: "Open Grafana drilldown" button

Wires the existing customer-drilldown dashboard JSON to the customer
detail page. Button opens ${Grafana.BaseUrl}/d/customer-drilldown
in a new tab with var-customer=<customer-id> pre-filled, kiosk mode,
light theme.

- Fetches /api/grafana/config (cached 5min, reuses the existing
  TanStack query key so GrafanaInfoCard's cache is shared).
- Button disabled with tooltip explaining when Grafana baseUrl isn't
  configured for the Admin stack (points to Settings → Grafana).
- Customer id is URI-encoded before interpolation (defence in depth —
  it's a UUID, but encodeURIComponent costs nothing).
- Dashboard UID hardcoded as 'customer-drilldown' to match the
  provisioned JSON. Renaming requires changing both together.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

portal/frontend/src/pages/AdminCustomerDetailPage.tsx

@@ -1,15 +1,20 @@
-import { Card, Descriptions, Tabs, Table, Tag, Typography, Button, Space, Spin, Result } from 'antd';
+import { Card, Descriptions, Tabs, Table, Tag, Typography, Button, Space, Spin, Result, Tooltip } from 'antd';
 import type { ColumnsType } from 'antd/es/table';
-import { ArrowLeftOutlined } from '@ant-design/icons';
+import { ArrowLeftOutlined, LineChartOutlined } from '@ant-design/icons';
 import { useQuery } from '@tanstack/react-query';
 import { useNavigate, useParams } from 'react-router-dom';
 import {
   fetchFleetCustomerDetail, type FleetSite, type FleetDevice,
   type FleetRecentMeasurement, type FleetIngestEvent,
 } from '../api/fleet';
+import { fetchGrafanaConfig } from '../api/grafana';
 
 const { Text } = Typography;
 
+// UID of the customer-drilldown dashboard provisioned in grafana/dashboards-admin/.
+// Coordinated change: rename here and in the JSON together.
+const CUSTOMER_DRILLDOWN_UID = 'customer-drilldown';
+
 export function AdminCustomerDetailPage() {
   const { id = '' } = useParams<{ id: string }>();
   const navigate = useNavigate();
@@ -18,6 +23,17 @@ export function AdminCustomerDetailPage() {
     queryFn: () => fetchFleetCustomerDetail(id),
     refetchInterval: 30_000,
   });
+  const { data: grafana } = useQuery({
+    queryKey: ['grafana-config'],
+    queryFn: fetchGrafanaConfig,
+    staleTime: 5 * 60_000,
+  });
+
+  const drilldownUrl = (() => {
+    if (!data || !grafana?.baseUrl) return null;
+    const base = grafana.baseUrl.replace(/\/$/, '');
+    return `${base}/d/${encodeURIComponent(CUSTOMER_DRILLDOWN_UID)}?orgId=1&kiosk=tv&theme=light&var-customer=${encodeURIComponent(data.id)}`;
+  })();
 
   if (isLoading) return <div style={{ textAlign: 'center', padding: 64 }}><Spin size="large" /></div>;
   if (error || !data) {
@@ -56,11 +72,29 @@ export function AdminCustomerDetailPage() {
 
   return (
     <Space direction="vertical" size="middle" style={{ width: '100%' }}>
+      <Space style={{ width: '100%', justifyContent: 'space-between' }}>
         <Space>
           <Button icon={<ArrowLeftOutlined />} onClick={() => navigate('/admin/customers')}>Customers</Button>
           <Text strong style={{ fontSize: 20 }}>{data.code} · {data.name}</Text>
           {data.isActive ? <Tag color="green">Active</Tag> : <Tag color="red">Disabled</Tag>}
         </Space>
+        <Tooltip
+          title={
+            drilldownUrl
+              ? `Opens the Grafana customer-drilldown dashboard with var-customer=${data.id}`
+              : 'Grafana base URL is not configured for this Admin stack — see Settings → Grafana.'
+          }
+        >
+          <Button
+            type="primary"
+            icon={<LineChartOutlined />}
+            disabled={!drilldownUrl}
+            onClick={() => drilldownUrl && window.open(drilldownUrl, '_blank', 'noopener')}
+          >
+            Open Grafana drilldown
+          </Button>
+        </Tooltip>
+      </Space>
 
       <Card size="small">
         <Descriptions column={3} size="small">