Forecasting app: hybrid port to HNF stack

Python FastAPI ML backend kept intact; auth replaced with central hnf_session cookie verification. Frontend rebuilt on React 18 + TS + Vite with stack design system, Plotly charts retained. Shared Postgres via DATABASE_URL; schema applied on startup.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/main.tsx

@@ -0,0 +1,20 @@
+import React from 'react'
+import ReactDOM from 'react-dom/client'
+import { BrowserRouter } from 'react-router-dom'
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import App from './App'
+import './index.css'
+
+const qc = new QueryClient({
+  defaultOptions: { queries: { retry: 1, staleTime: 30_000 } },
+})
+
+ReactDOM.createRoot(document.getElementById('root')!).render(
+  <React.StrictMode>
+    <BrowserRouter basename="/forecasting">
+      <QueryClientProvider client={qc}>
+        <App />
+      </QueryClientProvider>
+    </BrowserRouter>
+  </React.StrictMode>,
+)