Initial fullstack project setup with Next.js 15, Gin, PostgreSQL and Docker Compose

- Frontend: Next.js 15 (App Router), Auth.js v5, shadcn/ui, MagicUI
- Backend: Go + Gin + GORM with layered architecture
- Auth: Local credentials login with optional Keycloak OAuth binding
- Admin: RBAC user management for admin role
- Dev: Docker Compose with hot reload for both frontend and backend
- Docker: 3-service orchestration (frontend, backend, postgres)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/app/unauthorized/page.tsx

@@ -0,0 +1,11 @@
+export default function UnauthorizedPage() {
+  return (
+    <div className="flex min-h-screen flex-col items-center justify-center p-4">
+      <h1 className="text-3xl font-bold">403</h1>
+      <p className="mt-2 text-gray-500">您没有权限访问该页面</p>
+      <a href="/dashboard" className="mt-4 text-blue-600 hover:underline">
+        返回仪表盘
+      </a>
+    </div>
+  );
+}