refactor(backend): 存在確認のfindOneByをexistに置き換え (#11224)

* refactor(backend): 存在確認の`findOneBy`を`exist`に置き換え

* cleanup

packages/backend/src/server/api/endpoints/i/import-antennas.ts

@@ -66,8 +66,8 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 		private downloadService: DownloadService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
-			const users = await this.usersRepository.findOneBy({ id: me.id });
-			if (users === null) throw new ApiError(meta.errors.noSuchUser);
+			const userExist = await this.usersRepository.exist({ where: { id: me.id } });
+			if (!userExist) throw new ApiError(meta.errors.noSuchUser);
 			const file = await this.driveFilesRepository.findOneBy({ id: ps.fileId });
 			if (file === null) throw new ApiError(meta.errors.noSuchFile);
 			if (file.size === 0) throw new ApiError(meta.errors.emptyFile);