Cannot select Folia as artifact platform if enabled after project creation

### Is your feature request related to a problem? Yes. When publishing a version on Hangar, it is possible to upload multiple artifacts (one per platform). However, if Folia support was enabled after the project was initially created, the option to select Folia as a target platform is disabled when adding an artifact. This prevents publishing a Folia-specific artifact alongside a Paper artifact within the same version. ### Describe the solution you'd like. I would like the Folia platform option to be available when adding artifacts, regardless of when Folia support was enabled for the project. In other words, once Folia support is enabled, it should be possible to attach a Folia artifact to any new version, just like with Paper. ### Describe alternatives you've considered. - Publishing only a Paper artifact and relying on external likes for Folia, which is not always accurate or ideal. - Recreating the project with Folia enabled from the start, which is not feasible for existing projects. ### Other This seems particularly problematic for projects that add Folia support later in their lifecycle, which is likely a common case as Folia adoption increases.