refactor: serve non-resident buckets with the global CORS policy

The pre-authentication CORS lookup stays resident-only, so client-supplied
path segments still cause no metadata I/O and no cache growth. The
fail-closed states for startup, load failures, and the internal namespace
are gone: CORS is a browser response policy rather than an authorization
boundary, and failing closed only denied browser clients CORS headers while
bucket metadata was still loading. A bucket whose stored CORS document does
not parse still gets no CORS headers. This removes the loadFailed bookkeeping
and the unused GetCorsConfig, HasAllowedOrigin, and generic Update path for
CORS; tests use the CORS-specific writer.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PvgysXDmhPBBimCReYtA8q
Signed-off-by: Feng Ruohang <rh@vonng.com>

cmd/site-replication-status-accounting_test.go

@@ -69,12 +69,14 @@ func testSiteReplicationStatusAccountsPerSiteAndSurvivesMalformedConfig(obj Obje
 		bucketSSEConfig:        sseXML,
 		bucketQuotaConfigFile:  quotaJSON,
 		bucketPolicyConfig:     policyJSON,
-		bucketCorsConfig:       []byte(testSiteReplicationCORSDoc),
 	} {
 		if _, err := globalBucketMetadataSys.Update(ctx, localBucket, configFile, data); err != nil {
 			t.Fatalf("%s: update %s: %v", instanceType, configFile, err)
 		}
 	}
+	if _, err := updateLocalBucketCORSMetadata(ctx, obj, localBucket, []byte(testSiteReplicationCORSDoc)); err != nil {
+		t.Fatalf("%s: update %s: %v", instanceType, bucketCorsConfig, err)
+	}
 
 	encode := func(data []byte) *string {
 		encoded := base64.StdEncoding.EncodeToString(data)