fix: 关闭监听器时同时关闭 boss 与 worker 事件循环

ProxySessionListener.close() 原先等 boss 组 shutdownGracefully 完成后才开始关闭
worker 组。两组各自要等 2 秒静默期，所以每次 close 至少约 4 秒。测试用
close().get(5, SECONDS) 收尾，在较慢的 Gitea runner 上 SessionTransferTest 有两个
用例因此超时（run 14129）；本机 SessionTransferTest 每个用例也都在 4.16 秒以上，最慢
5.18 秒。

改为同时开始关闭两组，两者都结束后再完成 shutdown。各组仍保留默认静默期，关闭前已
提交的任务照常执行。本机 SessionTransferTest 单用例中位数 4.19 秒降到 2.15 秒，最慢
5.18 秒降到 3.13 秒。

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

proxy/core/src/main/java/dev/moonbridge/core/session/ProxySessionListener.java

@@ -34,6 +34,7 @@ import io.netty.channel.socket.SocketChannel;
 import io.netty.resolver.AddressResolverGroup;
 import io.netty.resolver.dns.DnsAddressResolverGroup;
 import io.netty.resolver.dns.DnsNameResolverBuilder;
+import io.netty.util.concurrent.Future;
 
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
@@ -512,7 +513,10 @@ public final class ProxySessionListener implements Players {
         allSessions.forEach(session -> session.closeBecause("proxy shutting down"));
         backendResolver.close();
         shutdown = new CompletableFuture<>();
-        boss.shutdownGracefully().addListener(first -> workers.shutdownGracefully().addListener(second -> {
+        // Start both at once: each group waits out its own quiet period, so draining them in turn doubled the close time.
+        Future<?> bossStopped = boss.shutdownGracefully();
+        Future<?> workersStopped = workers.shutdownGracefully();
+        bossStopped.addListener(first -> workersStopped.addListener(second -> {
             if (first.isSuccess() && second.isSuccess()) shutdown.complete(null);
             else shutdown.completeExceptionally(first.isSuccess() ? second.cause() : first.cause());
         }));