add createdAt column to game, group and player tables and DAOs

lib/data/db/tables/game_table.dart

@@ -6,6 +6,7 @@ class GameTable extends Table {
   TextColumn get name => text()();
   TextColumn get winnerId =>
       text().references(PlayerTable, #id, onDelete: KeyAction.cascade)();
+  DateTimeColumn get createdAt => dateTime()();
 
   @override
   Set<Column<Object>> get primaryKey => {id};

lib/data/db/tables/group_table.dart

@@ -3,6 +3,7 @@ import 'package:drift/drift.dart';
 class GroupTable extends Table {
   TextColumn get id => text()();
   TextColumn get name => text()();
+  DateTimeColumn get createdAt => dateTime()();
 
   @override
   Set<Column<Object>> get primaryKey => {id};

lib/data/db/tables/player_table.dart

@@ -3,6 +3,7 @@ import 'package:drift/drift.dart';
 class PlayerTable extends Table {
   TextColumn get id => text()();
   TextColumn get name => text()();
+  DateTimeColumn get createdAt => dateTime()();
 
   @override
   Set<Column<Object>> get primaryKey => {id};