fix docker defaults to writable /data config path and align docs

docker-compose.yml

@@ -9,8 +9,9 @@ services:
       # Host port is configurable via DS2API_HOST_PORT; container port stays fixed at 5001.
       - "${DS2API_HOST_PORT:-6011}:5001"
     volumes:
-      - ./config.json:/app/config.json    # 配置文件
+      - ./config.json:/data/config.json   # 配置文件（持久化推荐路径）
     environment:
       - TZ=Asia/Shanghai
       - LOG_LEVEL=INFO
       - DS2API_ADMIN_KEY=${DS2API_ADMIN_KEY:-ds2api}
+      - DS2API_CONFIG_PATH=/data/config.json