Enhance: 2段階認証時のリカバリーコードのファイル名にサーバーURLを含めるように (#15677)

* enhance(frontend): include server hostname and port in 2fa recovery code filename

* chore(frontend): fix mistake(use `@` for indicate server hostname)

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Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

packages/frontend/src/pages/settings/2fa.qrdialog.vue

@@ -106,6 +106,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 </template>
 
 <script lang="ts" setup>
+import { hostname, port } from '@@/js/config';
 import { useTemplateRef, ref } from 'vue';
 import MkButton from '@/components/MkButton.vue';
 import MkModalWindow from '@/components/MkModalWindow.vue';
@@ -161,7 +162,7 @@ function downloadBackupCodes() {
 		const txtBlob = new Blob([backupCodes.value.join('\n')], { type: 'text/plain' });
 		const dummya = document.createElement('a');
 		dummya.href = URL.createObjectURL(txtBlob);
-		dummya.download = `${$i.username}-2fa-backup-codes.txt`;
+		dummya.download = `${$i.username}@${hostname}` + (port !== '' ? `_${port}` : '') + '-2fa-backup-codes.txt';
 		dummya.click();
 	}
 }