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>

internal/bucket/cors/cors.go

@@ -290,12 +290,6 @@ func (r Rule) matchAllowedOrigin(origin string) (string, bool) {
 	return "", false
 }
 
-// HasAllowedOrigin reports whether the rule allows the given origin.
-func (r Rule) HasAllowedOrigin(origin string) bool {
-	_, ok := r.matchAllowedOrigin(origin)
-	return ok
-}
-
 // HasAllowedMethod reports whether the rule allows the given HTTP method.
 func (r Rule) HasAllowedMethod(method string) bool {
 	for _, m := range r.AllowedMethods {