refactor(web): drop 5 unused imports across 4 pages (CodeQL #6, #7, #8, #9)

Four CodeQL js/unused-local-variable alerts in one sweep — all
Note severity, all pure dead-import cleanup verified by grep
(each removed symbol had exactly 1 occurrence in its file: the
import line itself).

Alert #6 — web/src/pages/AgentFleetPage.tsx:3:
  Drop Legend from recharts named-import list. The fleet pie
  chart renders without a legend (the slice colors are labeled
  inline via Tooltip).

Alert #7 — web/src/pages/DashboardPage.tsx:9:
  Drop getAgents + getNotifications from the api/client named-
  import list. The dashboard summary card now uses
  getDashboardSummary (single endpoint) instead of fanning out
  to per-resource list calls; the agents + notifications full
  list is reachable via dedicated pages.

Alert #8 — web/src/pages/CertificatesPage.tsx:6:
  Drop revokeCertificate from the api/client named-import list.
  The page uses bulkRevokeCertificates for the multi-cert UX;
  single-cert revoke happens on CertificateDetailPage which
  imports revokeCertificate independently.

Alert #9 — web/src/pages/DiscoveryPage.tsx:15:
  Drop the StatusBadge default-import line. Discovered-cert
  status renders inline (text label colored via the row's
  state-class) without the StatusBadge component.

Verified locally:
  Each flagged symbol: 0 occurrences in its file post-edit.
  tsc --noEmit: exit 0.
  No behavioral change — pure import-list cleanup.

References:
  https://github.com/certctl-io/certctl/security/code-scanning/6
  https://github.com/certctl-io/certctl/security/code-scanning/7
  https://github.com/certctl-io/certctl/security/code-scanning/8
  https://github.com/certctl-io/certctl/security/code-scanning/9
Closes all four alerts.

web/src/pages/AgentFleetPage.tsx

@@ -1,6 +1,6 @@
 import { useQuery } from '@tanstack/react-query';
 import { useNavigate } from 'react-router-dom';
-import { PieChart, Pie, Cell, ResponsiveContainer, Tooltip, Legend } from 'recharts';
+import { PieChart, Pie, Cell, ResponsiveContainer, Tooltip } from 'recharts';
 import { getAgents } from '../api/client';
 import PageHeader from '../components/PageHeader';
 import StatusBadge from '../components/StatusBadge';

web/src/pages/CertificatesPage.tsx

@@ -3,7 +3,7 @@ import { useQuery, useQueryClient } from '@tanstack/react-query';
 import { useTrackedMutation } from '../hooks/useTrackedMutation';
 import { useListParams } from '../hooks/useListParams';
 import { useNavigate } from 'react-router-dom';
-import { getCertificates, createCertificate, revokeCertificate, getOwners, getTeams, getRenewalPolicies, getProfiles, getIssuers, bulkRevokeCertificates, bulkRenewCertificates, bulkReassignCertificates } from '../api/client';
+import { getCertificates, createCertificate, getOwners, getTeams, getRenewalPolicies, getProfiles, getIssuers, bulkRevokeCertificates, bulkRenewCertificates, bulkReassignCertificates } from '../api/client';
 import { useAuth } from '../components/AuthProvider';
 import { REVOCATION_REASONS } from '../api/types';
 import PageHeader from '../components/PageHeader';

web/src/pages/DashboardPage.tsx

@@ -7,7 +7,7 @@ import {
   XAxis, YAxis, CartesianGrid, Tooltip, ResponsiveContainer, Legend,
 } from 'recharts';
 import {
-  getCertificates, getAgents, getJobs, getNotifications, getHealth,
+  getCertificates, getJobs, getHealth,
   getDashboardSummary, getCertificatesByStatus, getExpirationTimeline,
   getJobTrends, getIssuanceRate, previewDigest, sendDigest, getIssuers,
 } from '../api/client';

web/src/pages/DiscoveryPage.tsx

@@ -12,7 +12,6 @@ import {
 import PageHeader from '../components/PageHeader';
 import DataTable from '../components/DataTable';
 import type { Column } from '../components/DataTable';
-import StatusBadge from '../components/StatusBadge';
 import ErrorState from '../components/ErrorState';
 import { formatDateTime } from '../api/utils';
 import type { DiscoveredCertificate, DiscoveryScan } from '../api/types';