feat(导航设置): 重构导航设置页面并优化通知队列管理

重构导航设置页面UI以匹配正式侧栏样式，增加拖拽排序功能。添加通知队列管理系统以防止通知重叠显示。更新最小启用导航项限制的提示信息。

Author: AyaxYuna

lib/src/core/navigation/navigation_settings_notifier.dart

@@ -8,7 +8,7 @@ import 'package:shared_preferences/shared_preferences.dart';
 import 'navigation_settings.dart';
 import 'navigation_item.dart';
 import 'navigation_element.dart';
-import '/src/shared/extensions/ui_extensions.dart';
+import '/src/shared/extensions/ui_extensions.dart';
 
 part 'navigation_settings_notifier.g.dart';
 
@@ -254,10 +254,10 @@ class NavigationSettingsNotifier extends _$NavigationSettingsNotifier {
     if (!isEnabled) {
       final tempState = state.value!.updateItemEnabled(itemId, false);
       if (tempState.getEnabledCount() < 2) {
-        // 至少需要两个导航项启用，显示提示并取消禁用操作
+        // Keep at least one non-user nav item (plus the fixed user item).
         ScaffoldMessenger.of(context).showTopSnackBar(
           SnackBar(
-            content: Text('至少需要启用两个导航项'),
+            content: Text('??????????? 1 ????'),
             duration: const Duration(seconds: 2),
             behavior: SnackBarBehavior.floating,
           ),