refactor!: rename the project from Monitor to MoShiro [CI]

Namespaces, assemblies, solution, binaries, images, systemd units, config paths, environment variables, protocol methods and the Linux user are all renamed. Breaking: existing databases, node identities and installed units must be recreated.

backend/src/MoShiro.Backend.Gateway/ConnectionShutdown.cs

@@ -0,0 +1,49 @@
+using Fleet.Server;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
+namespace MoShiro.Backend.Gateway;
+
+/// <summary>
+/// 宿主开始停止时先关闭所有 Agent 的长连接（Close 握手，不发 revoked：Agent 会重连）。
+/// 否则 Kestrel 的有序停止要等满 30 秒的超时，才会放弃这些永远不会自己结束的 WebSocket。
+/// </summary>
+public sealed class ConnectionShutdown : IHostedService
+{
+    private readonly IServiceProvider _services;
+    private readonly IHostApplicationLifetime _lifetime;
+    private Task? _closing;
+
+    public ConnectionShutdown(IServiceProvider services, IHostApplicationLifetime lifetime)
+    {
+        _services = services;
+        _lifetime = lifetime;
+    }
+
+    public Task StartAsync(CancellationToken cancellationToken)
+    {
+        // ApplicationStopping 在有序停止的最开始触发，早于 Kestrel 等待连接结束：这里不阻塞，关闭在后台进行，StopAsync 再等它做完
+        _lifetime.ApplicationStopping.Register(() => _closing = CloseAsync());
+        return Task.CompletedTask;
+    }
+
+    public async Task StopAsync(CancellationToken cancellationToken)
+    {
+        if (_closing is { } closing)
+        {
+            await closing.WaitAsync(TimeSpan.FromSeconds(5), cancellationToken);
+        }
+    }
+
+    private async Task CloseAsync()
+    {
+        try
+        {
+            await _services.GetRequiredService<IFleetConnections>().CloseAllAsync("server shutting down");
+        }
+        catch (Exception ex) when (ex is ObjectDisposedException or InvalidOperationException)
+        {
+            // 停止过程中，服务已经在释放：Kestrel 的超时兜底
+        }
+    }
+}