feat: add localisation

lib/database/app_database.dart

@@ -109,6 +109,8 @@ class AppSettingsTable extends Table {
 
   TextColumn get themeMode => text().withDefault(const Constant('system'))();
 
+  TextColumn get language => text().withDefault(const Constant('system'))();
+
   @override
   Set<Column> get primaryKey => {id};
 }
@@ -129,7 +131,7 @@ class AppDatabase extends _$AppDatabase {
   AppDatabase([QueryExecutor? executor]) : super(executor ?? _openConnection());
 
   @override
-  int get schemaVersion => 6;
+  int get schemaVersion => 7;
 
   @override
   MigrationStrategy get migration {
@@ -159,6 +161,10 @@ class AppDatabase extends _$AppDatabase {
         if (from < 6) {
           await migrator.addColumn(closedTabs, closedTabs.paymentMethod);
         }
+
+        if (from < 7) {
+          await migrator.addColumn(appSettingsTable, appSettingsTable.language);
+        }
       },
     );
   }