docker: nginx listens on 80 and 8890, backend moves to internal 8891

Deploy platforms that route to the container's exposed/compose port
(8890) were hitting the fun backend directly, which 404s unmatched
GET paths. Now nginx answers on both ports so either routing lands
on the SPA/API proxy layer.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

compose.yaml

@@ -4,7 +4,7 @@ services:
     image: cyi-box:latest
     container_name: cyibox
     ports:
-      - "8890:80"          # 对外端口，左侧可改成任意宿主端口
+      - "8890:8890"        # 对外端口：容器内 nginx 同时监听 80 与 8890，左侧随意改
     volumes:
       - cyibox-data:/app/data   # SQLite + vault.key + 网盘文件都落这里
     environment: