feat: add user role system and public joke submission API

- Add AdminUser role field (admin/submitter)
- User management in admin panel
- Public joke submission API (no auth required)
- Document submission methods for external workers

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

admin/src/router/index.js

@@ -20,12 +20,13 @@ const routes = [
       { path: 'links', name: 'LinkList', component: () => import('@/views/links/List.vue') },
       { path: 'links/edit/:id?', name: 'LinkEdit', component: () => import('@/views/links/Edit.vue') },
       { path: 'feedbacks', name: 'FeedbackList', component: () => import('@/views/feedback/List.vue') },
+      { path: 'users', name: 'UserList', component: () => import('@/views/user/List.vue') },
     ]
   }
 ]
 
 const router = createRouter({
-  history: createWebHistory(),
+  history: createWebHistory('/admin'),
   routes
 })