Scaffold @forte/admin package with React, Vite, shadcn/ui, TanStack Router

Sets up the admin frontend with login page, auth guard, API client, Zustand
auth store, and all shadcn/ui components. Vite proxies /v1 to backend in dev.

packages/admin/src/lib/query-client.ts

@@ -0,0 +1,11 @@
+import { QueryClient } from '@tanstack/react-query'
+
+export const queryClient = new QueryClient({
+  defaultOptions: {
+    queries: {
+      staleTime: 30_000,
+      retry: 1,
+      refetchOnWindowFocus: false,
+    },
+  },
+})