feedback7 G-TOOLS: listen on :: by default so one socket serves IPv6 and IPv4 (PR #291 by @LimitlessHPPK)

Ported only the dual-stack listen from PR #291 (the change accepted as #188). With HOST unset the server binds :: and, if that fails with EAFNOSUPPORT, EADDRNOTAVAIL or EINVAL, retries 0.0.0.0. An explicit HOST, including 0.0.0.0 and 127.0.0.1, is tried once. The boot banner and doctor list shareable IPv6 addresses in brackets, skip fe80::, and keep one URL per /64. An explicit IPv6 literal in the local URL is bracketed. The Windows service listing no longer drops those bracketed lines.

Not ported: /dev/grant, the settings-default migration, and the firewall scripts. The Docker image stays on 0.0.0.0; the alpine fallback was not booted.

Tests: node --test test/ipv6-bind.test.js test/doctor.test.js test/ci.test.js — 20 pass, 0 fail (8 bind, 4 doctor, 8 ci).

README.md

@@ -118,7 +118,7 @@ npm start          # 启动服务器：http://localhost:3000
 | 环境变量 | 默认 | 说明 |
 |---|---|---|
 | `PORT` | `3000` | 监听端口 |
-| `HOST` | `0.0.0.0` | 监听地址（`127.0.0.1` = 只允许本机，放在反向代理后面时使用） |
+| `HOST` | `::` | 监听地址。默认 `::` 是双栈：同一个端口同时接受 IPv6 和 IPv4；`0.0.0.0` = 只 IPv4；`127.0.0.1` = 只允许本机，放在反向代理后面时使用 |
 | `SP_COMBAT` | `client` | `client`：各玩家浏览器模拟自己的战斗（服务器负载极低）；`server`：由服务器模拟并推流 |
 | `SP_VERIFY` | `off` | 服务器复算客户端上报的战斗结果：`off` / `sample`（约 1/8 抽查）/ `all`（全部复算，更耗 CPU） |
 | `TRUST_PROXY` | `auto` | 是否信任 `X-Forwarded-For` 等转发头：`auto` 只信任来自本机 / 内网的代理；`1` 总是；`0` 从不 |