refactor: 项目稳定性优化

RestForm.cs

@@ -6,11 +6,11 @@ namespace TimerApp
 {
     public class RestForm : Form
     {
-        private Label lblMessage;
-        private Label lblTimer;
-        private Button btnSkip;
+        private Label lblMessage = null!;
+        private Label lblTimer = null!;
+        private Button btnSkip = null!;
 
-        public event EventHandler SkipRequested;
+        public event EventHandler? SkipRequested;
 
         public RestForm()
         {
@@ -99,12 +99,12 @@ namespace TimerApp
             this.PerformLayout();
         }
 
-        private void RestForm_Load(object sender, EventArgs e)
+        private void RestForm_Load(object? sender, EventArgs e)
         {
             CenterControls();
         }
 
-        private void RestForm_Resize(object sender, EventArgs e)
+        private void RestForm_Resize(object? sender, EventArgs e)
         {
             CenterControls();
         }
@@ -153,7 +153,7 @@ namespace TimerApp
             }
         }
 
-        private void btnSkip_Click(object sender, EventArgs e)
+        private void btnSkip_Click(object? sender, EventArgs e)
         {
             SkipRequested?.Invoke(this, EventArgs.Empty);
             this.Close();