[ui] #38: make the CORS setup helper provider-aware (R2 / B2 / Custom S3)

The first cut showed for Custom S3 too but always gave B2-only instructions (b2 CLI +
B2-native JSON), and was hidden for R2. Now the helper shows for all bucket providers
and tailors its content:

- Backblaze B2  -> B2-native rules + `b2 update-bucket --corsRules ...`
- Custom S3     -> standard S3 CORSConfiguration + `aws s3api put-bucket-cors
                   --endpoint-url <endpoint> ...`
- Cloudflare R2 -> standard S3 JSON + Cloudflare dashboard guidance (R2 -> bucket ->
                   Settings -> CORS Policy) and the AWS-CLI command vs the derived R2
                   endpoint.

Origins pre-filled from getCorsOrigins(); intro/command-label/notes set per provider;
copy buttons for both blocks. bitvid still auto-applies CORS on Save (R2/S3 via
ensureBucketCors) — this is the manual fallback when the key lacks CORS-write perms.

buildCorsHelpContent() switches on provider; modal text is now data-driven. Tests
extended to 10 (per-provider rules + command + a DOM provider-switch). Build + lint
clean; storage suites 40/40.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

js/ui/profileModal/ProfileStorageController.js

@@ -35,9 +35,12 @@ export class ProfileStorageController {
     this.storageR2Helper = null;
     this.storageB2Helper = null;
     this.storageS3Helper = null;
-    // CORS setup helper modal (B2 / Custom S3) — owns its own DOM + behavior.
+    // Provider-aware CORS setup helper modal — owns its own DOM + behavior.
     this.corsHelp = new StorageCorsHelp({
+      getProvider: () => this.storageProviderInput?.value || "cloudflare_r2",
       getBucket: () => this.storageBucketInput?.value?.trim() || "",
+      getRegion: () => this.storageRegionInput?.value?.trim() || "",
+      getEndpoint: () => this.storageEndpointInput?.value?.trim() || "",
     });
     this.storageForcePathStyleInput = null;
     this.storageForcePathStyleLabel = null;
@@ -447,7 +450,6 @@ export class ProfileStorageController {
       }
     }
 
-    // Region matters for B2 (drives the endpoint) and AWS-style S3; nudge the example.
     if (this.storageRegionInput && isB2) {
       this.storageRegionInput.placeholder = "us-west-004";
     } else if (this.storageRegionInput) {
@@ -480,8 +482,7 @@ export class ProfileStorageController {
       );
     }
 
-    // Manual CORS helper is for S3-compatible providers (B2 / Custom S3), not R2.
-    this.corsHelp.setVisible(!isR2);
+    this.corsHelp.setVisible(true); // provider-aware; useful for all bucket providers
   }
 
   getStorageUnlockFailureMessage(error) {
@@ -814,8 +815,7 @@ export class ProfileStorageController {
           secretAccessKey,
           bucket,
           forcePathStyle,
-          // Honor an explicit Public Access URL (custom domain / CDN); when blank,
-          // validateS3Connection derives it from the endpoint + bucket.
+          // Explicit Public Access URL (custom domain/CDN); blank → derived.
           publicBaseUrl: prefix || undefined,
           origins: getCorsOrigins(),
         });