Initial commit to new repository

src/AxCopilot/Services/SessionTrackingService.cs

@@ -0,0 +1,49 @@
+using Microsoft.Win32;
+
+namespace AxCopilot.Services;
+
+/// <summary>
+/// Windows 세션 잠금/해제 이벤트를 추적하여 PC 활성 시간을 기록합니다.
+/// </summary>
+public sealed class SessionTrackingService : IDisposable
+{
+    private DateTime? _unlockTime;
+    private bool _disposed;
+
+    public SessionTrackingService()
+    {
+        // 앱 시작 = 잠금 해제 상태로 간주
+        _unlockTime = DateTime.Now;
+        SystemEvents.SessionSwitch += OnSessionSwitch;
+    }
+
+    private void OnSessionSwitch(object sender, SessionSwitchEventArgs e)
+    {
+        if (e.Reason == SessionSwitchReason.SessionLock)
+        {
+            FlushActiveTime();
+        }
+        else if (e.Reason == SessionSwitchReason.SessionUnlock ||
+                 e.Reason == SessionSwitchReason.SessionLogon)
+        {
+            _unlockTime = DateTime.Now;
+        }
+    }
+
+    private void FlushActiveTime()
+    {
+        if (!_unlockTime.HasValue) return;
+        var seconds = (int)(DateTime.Now - _unlockTime.Value).TotalSeconds;
+        if (seconds > 0)
+            UsageStatisticsService.AddActiveSeconds(seconds);
+        _unlockTime = null;
+    }
+
+    public void Dispose()
+    {
+        if (_disposed) return;
+        _disposed = true;
+        FlushActiveTime();
+        SystemEvents.SessionSwitch -= OnSessionSwitch;
+    }
+}