feat(server): set exiftool process count (#16388)

exiftool concurrency control

server/test/repositories/metadata.repository.mock.ts

@@ -4,6 +4,7 @@ import { Mocked, vitest } from 'vitest';
 
 export const newMetadataRepositoryMock = (): Mocked<RepositoryInterface<MetadataRepository>> => {
   return {
+    setMaxConcurrency: vitest.fn(),
     teardown: vitest.fn(),
     readTags: vitest.fn(),
     writeTags: vitest.fn(),