refactor: 移除多租户和客户相关代码及功能

refactor: 统一状态字段为字符串类型并更新相关组件
refactor: 更新模型基类移除租户和客户相关字段
refactor: 简化数据权限控制逻辑
refactor: 优化类型注解使用Python 3.10+语法
refactor: 清理无用导入和注释
docs: 更新文档移除多租户相关内容

backend/app/scripts/data/sys_user.json

@@ -13,13 +13,9 @@
     "github_login": null,
     "wx_login": null,
     "qq_login": null,
-    "user_type": "0",
-    "salt": "123456",
     "dept_id": 1,
     "status": "0",
     "description": "超级管理员",
-    "tenant_id": 1,
-    "customer_id": null,
     "created_id": null,
     "updated_id": null
   }