factor:布局颜色重构

lib/widgets/todo_form.dart

@@ -36,6 +36,7 @@ class _TodoFormState extends State<TodoForm> {
 
     Widget buildTitle() {
       return Row(
+        mainAxisAlignment: MainAxisAlignment.center,
         children: [
           Icon(
             widget.isEditing ? Icons.edit_note : Icons.add_task,
@@ -322,7 +323,6 @@ class _TodoFormState extends State<TodoForm> {
         decoration: BoxDecoration(
           color: colors.surface,
           borderRadius: BorderRadius.circular(12),
-          border: Border.all(color: Colors.grey.shade300, width: 1),
         ),
         padding: EdgeInsets.all(12),
         child: Column(
@@ -362,7 +362,7 @@ class _TodoFormState extends State<TodoForm> {
     }
 
     return Padding(
-      padding: const EdgeInsets.all(16),
+      padding: const EdgeInsets.symmetric(vertical: 6, horizontal: 10),
       child: Column(
         mainAxisSize: MainAxisSize.min,
         children: [buildTitle(), SizedBox(height: 20), buildForm()],