M-029 Pass 1 batch 2: migrate 5 two-mutation pages to useTrackedMutation

Drains 10 more useMutation sites (52 -> 42). Each migration declares explicit

invalidates per the M-009 contract.

Pages migrated:

  - DashboardPage.tsx        previewDigest + sendDigest both 'noop' (read-only

                              preview / fire-and-forget email — no client cache impact)

  - DiscoveryPage.tsx        claim + dismiss both invalidate

                              [['discovered-certificates'], ['discovery-summary']]

  - NotificationsPage.tsx    markRead + requeue both invalidate [['notifications']]

  - TargetDetailPage.tsx     update + testConnection both invalidate [['target', id]]

  - TargetsPage.tsx          createTarget + deleteTarget both invalidate [['targets']]

Verification:

  legacy useMutation count   52 -> 42 (-10)

  useTrackedMutation count    4 -> 14 (+10)

Closes 14 of 56 sites toward M-029 Pass 1 completion.

web/src/pages/TargetsPage.tsx

@@ -1,6 +1,7 @@
 import { useState } from 'react';
 import { Link } from 'react-router-dom';
-import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
+import { useQuery, useQueryClient } from '@tanstack/react-query';
+import { useTrackedMutation } from '../hooks/useTrackedMutation';
 import { getTargets, createTarget, deleteTarget, getAgents } from '../api/client';
 import PageHeader from '../components/PageHeader';
 import DataTable from '../components/DataTable';
@@ -242,13 +243,14 @@ function CreateTargetWizard({ onClose, onSuccess }: { onClose: () => void; onSuc
     return result;
   };
 
-  const mutation = useMutation({
+  const mutation = useTrackedMutation({
     mutationFn: () => createTarget({
       name,
       type: targetType,
       agent_id: agentId,
       config: buildConfigPayload(),
     }),
+    invalidates: [['targets']],
     onSuccess: () => onSuccess(),
     onError: (err: Error) => setError(err.message),
   });
@@ -407,9 +409,9 @@ export default function TargetsPage() {
     queryFn: () => getTargets(),
   });
 
-  const deleteMutation = useMutation({
+  const deleteMutation = useTrackedMutation({
     mutationFn: deleteTarget,
-    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['targets'] }),
+    invalidates: [['targets']],
   });
 
   const columns: Column<Target>[] = [