Phase 1b: React Query + Vitest on client

- @tanstack/react-query v5 with QueryClientProvider at app root
- client/src/api/queries.ts: query-key factory, hooks for tickets, ticket, audit,
  comments, users, CTI tree + cascade, plus full mutation set
  (create/update/delete ticket, add/delete comment, CTI CRUD, user CRUD)
- All page-level useEffect + useState fetching replaced:
  Dashboard, MyTickets, TicketDetail, NewTicket, admin/CTI, admin/Users
- Dashboard preserves 300ms debounced search via separate debouncedSearch state
- CTISelect cascades via useCategories / useTypes(categoryId) / useItems(typeId);
  dependent hooks disabled until parent selected
- vitest + @testing-library/react + jsdom; 6 client tests cover SeverityBadge + StatusBadge

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

client/src/main.tsx

@@ -1,10 +1,14 @@
 import { StrictMode } from 'react';
 import { createRoot } from 'react-dom/client';
+import { QueryClientProvider } from '@tanstack/react-query';
+import { queryClient } from './api/queryClient';
 import './index.css';
 import App from './App';
 
 createRoot(document.getElementById('root')!).render(
   <StrictMode>
-    <App />
+    <QueryClientProvider client={queryClient}>
+      <App />
+    </QueryClientProvider>
   </StrictMode>,
 );