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/_authenticated.tsx

@@ -0,0 +1,30 @@
+import { createFileRoute, Outlet, redirect } from '@tanstack/react-router'
+import { useAuthStore } from '@/stores/auth.store'
+
+export const Route = createFileRoute('/_authenticated')({
+  beforeLoad: () => {
+    const { token } = useAuthStore.getState()
+    if (!token) {
+      throw redirect({ to: '/login' })
+    }
+  },
+  component: AuthenticatedLayout,
+})
+
+function AuthenticatedLayout() {
+  return (
+    <div className="min-h-screen bg-background text-foreground">
+      <div className="flex">
+        <nav className="w-56 border-r border-border bg-sidebar min-h-screen p-4 space-y-2">
+          <h2 className="text-lg font-semibold text-sidebar-foreground mb-4">Forte</h2>
+          <a href="/accounts" className="block px-3 py-2 rounded-md text-sm text-sidebar-foreground hover:bg-sidebar-accent">
+            Accounts
+          </a>
+        </nav>
+        <main className="flex-1 p-6">
+          <Outlet />
+        </main>
+      </div>
+    </div>
+  )
+}