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/fleet/src/Fleet.Hosting/RestartController.cs

@@ -0,0 +1,73 @@
+namespace Fleet.Hosting;
+
+/// <summary>
+/// 当前生效的定时重启：节点本地的设置优先；本地没有写时用面板下发的，面板改了之后立即重新排下一次，不需要重启进程。
+/// </summary>
+public sealed class RestartController : IDisposable
+{
+    private readonly RestartSchedule? _local;
+    private readonly object _gate = new();
+    private RestartSchedule? _remote;
+    private CancellationTokenSource _changed = new();
+
+    public RestartController(RestartSchedule? local = null)
+    {
+        _local = local;
+    }
+
+    /// <summary>本地有设置时为 true：面板下发的不生效。</summary>
+    public bool IsLocal => _local is not null;
+
+    public RestartSchedule? Current
+    {
+        get
+        {
+            lock (_gate)
+            {
+                return _local ?? _remote;
+            }
+        }
+    }
+
+    /// <summary>当前设置被改动时会被取消的令牌；先取令牌、再取 <see cref="Current"/>，就不会漏掉中间的改动。</summary>
+    public CancellationToken ChangeToken
+    {
+        get
+        {
+            lock (_gate)
+            {
+                return _changed.Token;
+            }
+        }
+    }
+
+    /// <summary>面板下发的设置；为空表示面板关闭了定时重启。返回 false 表示文本不合法（节点忽略它）。</summary>
+    public bool SetRemote(string? text)
+    {
+        RestartSchedule? schedule = null;
+        if (!string.IsNullOrWhiteSpace(text) && !RestartSchedule.TryParse(text, out schedule))
+        {
+            return false;
+        }
+
+        CancellationTokenSource previous;
+        lock (_gate)
+        {
+            _remote = schedule;
+            previous = _changed;
+            _changed = new CancellationTokenSource();
+        }
+
+        previous.Cancel();
+        previous.Dispose();
+        return true;
+    }
+
+    public void Dispose()
+    {
+        lock (_gate)
+        {
+            _changed.Dispose();
+        }
+    }
+}