feat: rebuild fiscal clone architecture and harden coolify deployment

frontend/hooks/use-auth-guard.ts

@@ -0,0 +1,22 @@
+'use client';
+
+import { useEffect } from 'react';
+import { useRouter } from 'next/navigation';
+import { useSession } from '@/lib/better-auth';
+
+export function useAuthGuard() {
+  const { data: session, isPending } = useSession();
+  const router = useRouter();
+
+  useEffect(() => {
+    if (!isPending && !session) {
+      router.replace('/auth/signin');
+    }
+  }, [isPending, session, router]);
+
+  return {
+    session,
+    isPending,
+    isAuthenticated: Boolean(session?.user)
+  };
+}