refactor: 移除媒体检测逻辑，简化代码体积

MainForm.cs

@@ -25,10 +25,6 @@ namespace TimerApp
         public static extern bool ReleaseCapture();
         [DllImport("user32.dll")]
         public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);
-        [DllImport("user32.dll")]
-        static extern bool CreateCaret(IntPtr hWnd, IntPtr hBitmap, int nWidth, int nHeight);
-        [DllImport("user32.dll")]
-        static extern bool ShowCaret(IntPtr hWnd);
 
         private const int WM_NCLBUTTONDOWN = 0xA1;
         private const int HT_CAPTION = 0x2;
@@ -611,6 +607,7 @@ namespace TimerApp
         private void toolStripMenuItemExit_Click(object sender, EventArgs e)
         {
             _monitor.Stop();
+            _monitor.Dispose();
             notifyIcon1.Visible = false;
             notifyIcon1.Dispose();
             Application.Exit();