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.spec.ts

@@ -505,6 +505,7 @@ describe(AssetMediaService.name, () => {
       await expect(sut.downloadOriginal(authStub.admin, 'asset-1')).resolves.toEqual(
         new ImmichFileResponse({
           path: '/original/path.jpg',
+          fileName: 'asset-id.jpg',
           contentType: 'image/jpeg',
           cacheControl: CacheControl.PrivateWithCache,
         }),

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,
     });