fix: SSR crash — QueryClient in useState, mounted guard for auth hydration

components/providers.tsx

@@ -1,10 +1,19 @@
 'use client';
 
-import { QueryClientProvider } from '@tanstack/react-query';
-import { queryClient } from '@/lib/query-client';
+import { useState } from 'react';
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
 import { Toaster } from '@/components/ui/sonner';
 
 export default function Providers({ children }: { children: React.ReactNode }) {
+  // Must be created inside component — NOT at module level
+  // Module-level singleton causes SSR crashes in Next.js App Router
+  const [queryClient] = useState(
+    () =>
+      new QueryClient({
+        defaultOptions: { queries: { staleTime: 30_000, retry: 1 } },
+      })
+  );
+
   return (
     <QueryClientProvider client={queryClient}>
       {children}