fix: sort of completed tasks (#297)

ui/flutter/lib/api/model/task.dart

@@ -13,6 +13,7 @@ class Task {
   Status status;
   Progress progress;
   DateTime createdAt;
+  DateTime updatedAt;
 
   Task({
     required this.id,
@@ -20,6 +21,7 @@ class Task {
     required this.status,
     required this.progress,
     required this.createdAt,
+    required this.updatedAt,
   });
 
   factory Task.fromJson(Map<String, dynamic> json) => _$TaskFromJson(json);

ui/flutter/lib/api/model/task.g.dart

@@ -12,6 +12,7 @@ Task _$TaskFromJson(Map<String, dynamic> json) => Task(
       status: $enumDecode(_$StatusEnumMap, json['status']),
       progress: Progress.fromJson(json['progress'] as Map<String, dynamic>),
       createdAt: DateTime.parse(json['createdAt'] as String),
+      updatedAt: DateTime.parse(json['updatedAt'] as String),
     );
 
 Map<String, dynamic> _$TaskToJson(Task instance) => <String, dynamic>{
@@ -20,6 +21,7 @@ Map<String, dynamic> _$TaskToJson(Task instance) => <String, dynamic>{
       'status': _$StatusEnumMap[instance.status]!,
       'progress': instance.progress.toJson(),
       'createdAt': instance.createdAt.toIso8601String(),
+      'updatedAt': instance.updatedAt.toIso8601String(),
     };
 
 const _$StatusEnumMap = {