feat:重构代办事项模块

lib/models/todo.dart

@@ -0,0 +1,68 @@
+import 'package:flutter/material.dart';
+
+class TodoItem {
+  String id;
+  String title;
+  String? description;
+  bool isCompleted;
+  DateTime createdAt;
+  DateTime? dueDate;
+  TodoPriority priority;
+  String? category;
+
+  TodoItem({
+    required this.id,
+    required this.title,
+    this.description,
+    this.isCompleted = false,
+    DateTime? createdAt,
+    this.dueDate,
+    this.priority = TodoPriority.medium,
+    this.category,
+  }) : createdAt = createdAt ?? DateTime.now();
+
+  TodoItem copyWith({
+    String? id,
+    String? title,
+    String? description,
+    bool? isCompleted,
+    DateTime? createdAt,
+    DateTime? dueDate,
+    TodoPriority? priority,
+    String? category,
+  }) {
+    return TodoItem(
+      id: id ?? this.id,
+      title: title ?? this.title,
+      description: description ?? this.description,
+      isCompleted: isCompleted ?? this.isCompleted,
+      createdAt: createdAt ?? this.createdAt,
+      dueDate: dueDate ?? this.dueDate,
+      priority: priority ?? this.priority,
+      category: category ?? this.category,
+    );
+  }
+}
+
+enum TodoPriority {
+  low('低', Color(0xFF757575), Icons.low_priority),
+  medium('中', Color(0xFFF57C00), Icons.flag),
+  high('高', Color(0xFFD32F2F), Icons.warning);
+
+  final String label;
+  final Color color;
+  final IconData icon;
+
+  const TodoPriority(this.label, this.color, this.icon);
+}
+
+enum TodoTab {
+  all('全部'),
+  active('待完成'),
+  completed('已完成'),
+  today('今天');
+
+  final String label;
+
+  const TodoTab(this.label);
+}