feat(frontend): bootstrap Vite + React 19 + TS strict toolchain (F0.1)

- Vite 8 / React 19 / TS 6 strict (noUncheckedIndexedAccess, no baseUrl deprecation)
- Tailwind 4 via @tailwindcss/vite (no PostCSS step)
- TanStack Query 5, react-router-dom 7, Recharts, clsx
- Vitest + Testing Library + jsdom for unit tests
- Playwright skeleton + first smoke spec (login redirect)
- ESLint flat config: typescript-eslint type-checked, react-hooks, react-refresh, prettier
- Prettier config (semi, single quotes, 100-col, lf)
- IBM Plex font @font-face declarations targeting /fonts/ (self-host, no CDN — OPSEC)

frontend/src/App.tsx

@@ -0,0 +1,22 @@
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
+import { RouterProvider } from 'react-router-dom';
+import { router } from './router';
+
+const queryClient = new QueryClient({
+  defaultOptions: {
+    queries: {
+      staleTime: 30_000,
+      gcTime: 5 * 60_000,
+      retry: 1,
+      refetchOnWindowFocus: false,
+    },
+  },
+});
+
+export function App() {
+  return (
+    <QueryClientProvider client={queryClient}>
+      <RouterProvider router={router} />
+    </QueryClientProvider>
+  );
+}

frontend/src/main.tsx

@@ -0,0 +1,15 @@
+import { StrictMode } from 'react';
+import { createRoot } from 'react-dom/client';
+import './styles/globals.css';
+import { App } from './App';
+
+const container = document.getElementById('root');
+if (!container) {
+  throw new Error('Root element #root missing in index.html');
+}
+
+createRoot(container).render(
+  <StrictMode>
+    <App />
+  </StrictMode>,
+);

frontend/src/test/setup.ts

@@ -0,0 +1 @@
+import '@testing-library/jest-dom/vitest';