add copyright text to all our files

packages/backend/migration/1695937489995-enableAchievements.js

@@ -1,3 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: marie and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 export class EnableAchievements1695937489995 {
     name = 'EnableAchievements1695937489995'
 
@@ -8,4 +13,4 @@ export class EnableAchievements1695937489995 {
     async down(queryRunner) {
         await queryRunner.query(`ALTER TABLE "meta" DROP COLUMN "enableAchievements"`);
     }
-}
+}