When saving an R2 storage connection, the "Prefix" input (which holds the Public Bucket URL) was not being mapped to `meta.baseDomain` or `meta.publicBaseUrl`. This caused `R2Service.ensureBucketConfigForNpub` to throw "Public Bucket URL is missing" during upload preparation, as it relies on these properties.
This commit updates `ProfileModalController.handleSaveStorage` to correctly assign the prefix value to `baseDomain` and `publicBaseUrl` for the `cloudflare_r2` provider, aligning it with the behavior for generic S3 providers and resolving the upload error.