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/routes/__root.tsx

@@ -0,0 +1,15 @@
+import { createRootRoute, Outlet } from '@tanstack/react-router'
+import { Toaster } from 'sonner'
+
+export const Route = createRootRoute({
+  component: RootLayout,
+})
+
+function RootLayout() {
+  return (
+    <>
+      <Outlet />
+      <Toaster position="bottom-right" />
+    </>
+  )
+}