refactor(admin): 合并管理后台并移除 apps/agent

- 平台与代理共用 apps/admin，统一登录 manage/auth/login
- 按 userType 展示菜单，修复 token 循环跳转
- 删除独立 apps/agent 前端工程

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/admin/src/views/agent/SubAgents.vue

@@ -0,0 +1,39 @@
+<script setup lang="ts">
+import { ref, onMounted } from 'vue';
+import api from '../../api';
+import { ElMessage } from 'element-plus';
+
+const agents = ref<unknown[]>([]);
+const form = ref({ username: '', password: 'Agent@123', creditLimit: 10000 });
+
+onMounted(load);
+
+async function load() {
+  const { data } = await api.get('/agent/agents');
+  agents.value = data.data;
+}
+
+async function create() {
+  await api.post('/agent/agents', form.value);
+  ElMessage.success('下级代理已创建');
+  load();
+}
+</script>
+
+<template>
+  <h2>下级代理（仅一级代理可见）</h2>
+  <el-form inline style="margin-bottom: 16px">
+    <el-input v-model="form.username" placeholder="用户名" />
+    <el-input-number v-model="form.creditLimit" />
+    <el-button type="primary" @click="create">创建二级代理</el-button>
+  </el-form>
+  <el-table :data="agents">
+    <el-table-column label="用户名">
+      <template #default="{ row }">
+        {{ (row as { user?: { username: string } }).user?.username }}
+      </template>
+    </el-table-column>
+    <el-table-column prop="creditLimit" label="额度" />
+    <el-table-column prop="usedCredit" label="已用" />
+  </el-table>
+</template>