统一角色体系为admin/agent/user，修复代理查询角色错误，添加语言切换和明暗切换

frontend/src/router/guard/index.ts

@@ -19,10 +19,14 @@ export function createRouterGuard(router: Router) {
     const isAuthPage = to.path === '/login' || to.path === '/register'
 
     if (requiresAuth && !token) {
-      return '/login'
+      return { path: '/login', query: { redirect: to.fullPath } }
     }
 
     if (isAuthPage && token && user) {
+      const redirect = (to.query.redirect as string) || ''
+      if (redirect) {
+        return redirect
+      }
       if (user.role === 'agent' || user.parent_agent_id) {
         return '/agent'
       }

frontend/src/router/routes.ts

@@ -26,7 +26,7 @@ const routes: RouteRecordRaw[] = [
   {
     path: '/developer',
     component: () => import('@/layouts/developer.vue'),
-    meta: { auth: true, role: 'developer' },
+    meta: { auth: true, role: 'admin' },
     children: [
       {
         path: '',