v1.2.0: 重构为插件+独立Manager架构，横版UI，精确保留文本框边距的文档转换

Manager/ActivateDialog.xaml.cs

@@ -0,0 +1,27 @@
+using System.Windows;
+
+namespace BetterSeewo.Manager
+{
+    public partial class ActivateDialog : Window
+    {
+        public string LicenseKey { get; private set; } = "";
+
+        public ActivateDialog()
+        {
+            InitializeComponent();
+        }
+
+        private void OnKeyTextChanged(object sender, System.Windows.Controls.TextChangedEventArgs e)
+        {
+            ActivateButton.IsEnabled = KeyTextBox.Text.Trim().Length >= 4;
+        }
+
+        private void Activate_Click(object sender, RoutedEventArgs e)
+        {
+            LicenseKey = KeyTextBox.Text.Trim();
+            DialogResult = true;
+            Close();
+        }
+    }
+}
+