fix(storage): ensure R2 public URL is saved to connection metadata

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.

js/ui/profileModalController.js

@@ -9224,6 +9224,9 @@ export class ProfileModalController {
     // We can store it in meta if we want to show it in UI without decrypting.
     if (provider === "cloudflare_r2") {
         meta.accountId = endpointOrAccount;
+        // For R2, the "Prefix" input serves as the Public Base URL (e.g. https://pub-xxx.r2.dev)
+        meta.publicBaseUrl = prefix;
+        meta.baseDomain = prefix;
     } else {
         meta.publicBaseUrl = publicBaseUrl;
         meta.baseDomain = publicBaseUrl;