fix: keep nginx vars when envsubst fills A_UPSTREAM [deploy]

Dockerfile

@@ -3,6 +3,8 @@ FROM nginx:1.27-alpine
 
 # 集群内 A 站地址，可被 K8s env 覆盖
 ENV A_UPSTREAM=http://project57-deploy.ns-project57.svc.cluster.local:3000
+# 只替换 A_UPSTREAM，避免 envsubst 把 nginx 的 $host/$uri 等变量清空导致容器起不来
+ENV NGINX_ENVSUBST_FILTER=A_UPSTREAM
 
 COPY nginx.conf /etc/nginx/templates/default.conf.template
 COPY dist /usr/share/nginx/html