refactor: 移除 docker 目录，中间件编排收敛至根目录 docker-compose.yml

- docker-compose.yml 移至根目录，my.cnf/redis.conf 配置内联为 command 参数，数据持久化改用命名卷
- 删除 docker/ 目录（含运行时残留数据），清理 .gitignore 相关规则
- 同步 README 目录结构说明

README.en.md

@@ -201,8 +201,6 @@ Detailed guide: https://www.youlai.tech/docs/server/spring-boot/quick-start.html
 
 youlai-boot/
 
-├── docker/                    # Docker orchestration
-
 ├── docs/                      # Docs and image assets
 
 ├── sql/                       # Database init scripts
@@ -237,6 +235,8 @@ youlai-boot/
 
 │   └── system/                # Business (user/role/menu/dept/dict etc.)
 
+├── docker-compose.yml         # One-click middleware orchestration (MySQL/Redis/MinIO/Xxl-Job)
+
 └── pom.xml                    # Maven dependency management
 
 ```