fix: send filename when viewing the original file (#20005)

* feat: add fileName to downloadOriginal response

* test: add fileName to ImmichFileResponse for downloadOriginal

* lint: use single quotes for fileName string in test

server/src/services/asset-media.service.ts

@@ -197,6 +197,7 @@ export class AssetMediaService extends BaseService {
 
     return new ImmichFileResponse({
       path: asset.originalPath,
+      fileName: asset.originalFileName,
       contentType: mimeTypes.lookup(asset.originalPath),
       cacheControl: CacheControl.PrivateWithCache,
     });