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/stores/auth.ts

@@ -0,0 +1,84 @@
+import { ref, computed } from 'vue';
+
+export type StaffUserType = 'ADMIN' | 'AGENT';
+
+export interface StaffUser {
+  id: string;
+  username: string;
+  userType: StaffUserType;
+  locale?: string;
+  role?: string;
+}
+
+const TOKEN_KEY = 'manage_token';
+const USER_KEY = 'manage_user';
+
+function loadUser(): StaffUser | null {
+  try {
+    const raw = localStorage.getItem(USER_KEY);
+    return raw ? (JSON.parse(raw) as StaffUser) : null;
+  } catch {
+    return null;
+  }
+}
+
+function migrateLegacyTokens() {
+  if (localStorage.getItem(TOKEN_KEY)) return;
+  const legacyAdmin = localStorage.getItem('admin_token');
+  const legacyAgent = localStorage.getItem('agent_token');
+  if (legacyAdmin) {
+    localStorage.setItem(TOKEN_KEY, legacyAdmin);
+    localStorage.setItem(USER_KEY, JSON.stringify({ userType: 'ADMIN' }));
+    localStorage.removeItem('admin_token');
+    return;
+  }
+  if (legacyAgent) {
+    localStorage.setItem(TOKEN_KEY, legacyAgent);
+    localStorage.setItem(USER_KEY, JSON.stringify({ userType: 'AGENT' }));
+    localStorage.removeItem('agent_token');
+  }
+}
+
+migrateLegacyTokens();
+
+const token = ref(localStorage.getItem(TOKEN_KEY) || '');
+const user = ref<StaffUser | null>(loadUser());
+
+export function clearStaffSession() {
+  token.value = '';
+  user.value = null;
+  localStorage.removeItem(TOKEN_KEY);
+  localStorage.removeItem(USER_KEY);
+  localStorage.removeItem('admin_token');
+  localStorage.removeItem('agent_token');
+}
+
+export function useAuthStore() {
+  const isAdmin = computed(() => user.value?.userType === 'ADMIN');
+  const isAgent = computed(() => user.value?.userType === 'AGENT');
+  const portalLabel = computed(() => (isAdmin.value ? '平台后台' : '代理后台'));
+
+  function setSession(newToken: string, newUser: StaffUser) {
+    token.value = newToken;
+    user.value = newUser;
+    localStorage.setItem(TOKEN_KEY, newToken);
+    localStorage.setItem(USER_KEY, JSON.stringify(newUser));
+    localStorage.removeItem('admin_token');
+    localStorage.removeItem('agent_token');
+  }
+
+  function logout() {
+    clearStaffSession();
+  }
+
+  return {
+    token,
+    user,
+    isAdmin,
+    isAgent,
+    portalLabel,
+    setSession,
+    logout,
+    clearStaffSession,
+  };
+}