Resetting backup retention amount on volume backups to undefined (= unlimited) does not work

To Reproduce

1. Create a volume backup for a service (in my case a docker compose)
2. Set the "Keep Latest Backups" to a positive non-zero integer and save
3. Reload the page
4. Edit the volume and clear the "Keep Latest Backup" field and save
5. Reload the page

You will see, that the backup limit is still set to the positive integer (can be seen by editing the volume backup)

Current vs. Expected behavior

I expect the retention amount to be reset to no value (undefined) and my backups to be kept indefinetly

Current behavior: The retention amount doesn't get updated when setting it to undefined. (Page reload required to see the actual value).

AFAIK is there no way to turn of the limit once it was set.

Provide environment information

OS: Mac 15.6
Dokploy 0.28.8
Ubuntu VPS
Connection via https

Which area(s) are affected? (Select all that apply)

Application

Are you deploying the applications where Dokploy is installed or on a remote server?

Same server where Dokploy is installed

Additional context

No response

Will you send a PR to fix it?

No

Start by reproducing the volume-backup flow described in the issue: set “Keep Latest Backups,” then clear it and save. Trace the volume backup settings form and its save/update request to see how an undefined value is handled. Done means clearing the field persists after reload and backups are retained indefinitely.