feat: use simpler nitro instead of nestjs to implement mock service

apps/backend-mock/routes/[...].ts

@@ -0,0 +1,12 @@
+export default defineEventHandler(() => {
+  return `
+<h1>Hello Vben Admin</h1>
+<h2>Mock service is starting</h2>
+<ul>
+<li><a href="/api/user">/api/user/info</a></li>
+<li><a href="/api/menu">/api/menu/all</a></li>
+<li><a href="/api/auth/codes">/api/auth/codes</a></li>
+<li><a href="/api/auth/login">/api/auth/login</a></li>
+</ul>
+`;
+});