Add content length for downloading file

bubble-server/src/main/java/bubble/resources/cloud/NetworkActionsResource.java

@@ -192,6 +192,7 @@ public class NetworkActionsResource {
         final var outFileName = network.getNickname() + "." + backupId + (empty(passphrase) ? ".zip" : "");
 
         return send(new FileSendableResource(backupArchive).setContentType(APPLICATION_OCTET_STREAM)
+                                                           .setContentLength(backupArchive.length())
                                                            .setForceDownload(true)
                                                            .setName(outFileName));
     }