use clock.now() instead of DateTime.now() for DTO creation timestamps

lib/data/dto/game.dart

@@ -1,3 +1,4 @@
+import 'package:clock/clock.dart';
 import 'package:game_tracker/data/dto/group.dart';
 import 'package:game_tracker/data/dto/player.dart';
 import 'package:uuid/uuid.dart';
@@ -18,7 +19,7 @@ class Game {
     this.group,
     this.winner = '',
   }) : id = id ?? const Uuid().v4(),
-       createdAt = createdAt ?? DateTime.now();
+       createdAt = createdAt ?? clock.now();
 
   @override
   String toString() {

lib/data/dto/group.dart

@@ -1,3 +1,4 @@
+import 'package:clock/clock.dart';
 import 'package:game_tracker/data/dto/player.dart';
 import 'package:uuid/uuid.dart';
 
@@ -13,7 +14,7 @@ class Group {
     required this.name,
     required this.members,
   }) : id = id ?? const Uuid().v4(),
-       createdAt = createdAt ?? DateTime.now();
+       createdAt = createdAt ?? clock.now();
 
   @override
   String toString() {

lib/data/dto/player.dart

@@ -1,3 +1,4 @@
+import 'package:clock/clock.dart';
 import 'package:uuid/uuid.dart';
 
 class Player {
@@ -7,7 +8,7 @@ class Player {
 
   Player({String? id, DateTime? createdAt, required this.name})
     : id = id ?? const Uuid().v4(),
-      createdAt = createdAt ?? DateTime.now();
+      createdAt = createdAt ?? clock.now();
 
   @override
   String toString() {