refactor: 重构 API 层目录结构 & 样式模块化拆分

- API 层按业务域拆分（api/auth/, api/file/, api/system/*）
- 类型定义从 types/api/ 移入对应 api 模块内（就近原则）
- 公共类型统一为 api/common.ts，移除冗余类型重导出
- 样式文件按职责拆分（base/, layout/, vendors/），移除 common.scss
- 移除失效的单元测试文件

src/views/demo/curd/config/edit.ts

@@ -1,5 +1,5 @@
 import UserAPI from "@/api/system/user";
-import type { UserForm } from "@/types/api";
+import type { UserForm } from "@/api/system/user";
 import type { IModalConfig } from "@/components/CURD/types";
 import { DeviceEnum } from "@/enums/settings";
 import { useAppStore } from "@/store";