feat: daily node restart controlled from the admin, connect timings as a default line task [CI]

Agents and Probes exit in order at a configured time (default 04:30 UTC+8, switch and time zone in the admin settings) and the service manager starts them again; a local restart_at or MOSHIRO_RESTART_AT wins. The connect kind (TCP connect and TLS handshake timings) is now a default continuous line template, with a section on the line page.

backend/src/MoShiro.Backend.Application/Ports/IAgentGateway.cs

@@ -33,6 +33,9 @@ public interface IAgentGateway
     /// <summary>把发布清单和签名原样交给节点（通知，不等回复）。</summary>
     ValueTask NotifyUpdateOfferAsync(NodeId node, string manifest, string signature, CancellationToken ct);
 
+    /// <summary>把定时重启设置交给节点（通知，不等回复）；<paramref name="restartAt"/> 为空表示关闭。</summary>
+    ValueTask NotifyScheduleAsync(NodeId node, string? restartAt, CancellationToken ct);
+
     /// <summary>请求节点更新到它手里的清单。节点不在线返回 false。</summary>
     ValueTask<bool> NotifyUpdateApplyAsync(NodeId node, CancellationToken ct);
 }