fix(deploy): runtime DNS re-resolution via resolv.conf-injected resolver, both runtimes

deploy/nginx.conf

@@ -1,10 +1,13 @@
 server {
   listen 80;
   client_max_body_size 200m;
+  # 地址为占位默认值(127.0.0.11=Docker 内嵌 DNS);镜像 entrypoint 启动时会按
+  # /etc/resolv.conf 的首个 nameserver 重写本行,兼容 podman aardvark-dns。
+  resolver 127.0.0.11 valid=10s;
 
   location /api/ {
-    # 静态主机名:启动时经 /etc/resolv.conf 解析(Docker 127.0.0.11 / podman aardvark 均兼容)
-    proxy_pass http://api:8080;      # 无 URI 部分:保留 /api 前缀转发
+    set $api_upstream http://api:8080;   # 变量式 → 每次按 DNS 解析,scale 后轮询到新副本(spec §11)
+    proxy_pass $api_upstream;            # 无 URI 部分:保留 /api 前缀转发
     proxy_set_header Host $host;
     proxy_set_header X-Real-IP $remote_addr;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;