feat(ops): add object storage management and site-mapping CSV import/export

Ship the Ops backstage 对象存储 page (browse / upload / move / delete /
folder ops) backed by a new object-storage service + handler, with the
shared storage client extended with List/Stat/Copy/Usage/DownloadURL so
both MinIO and Aliyun providers cover the new surface. Add
ForcePathStyle to the object-storage config and treat r2/s3/custom_s3
as external providers so Cloudflare R2 and other S3-compatibles can
share the MinIO client path without spinning up the bundled MinIO.

Also add CSV import/export + template download to the site-domain
mappings page, raise gin MaxMultipartMemory to 8 MiB for the new
multipart endpoints, register Ops swagger routes, and extend the
descriptions-parity test to cover the ops router.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

deploy/scripts/load-and-start.sh

@@ -115,7 +115,7 @@ use_minio_for_object_storage() {
     ""|minio|mino)
       return 0
       ;;
-    aliyun|aliyun_oss|aliyun-oss|oss)
+    aliyun|aliyun_oss|aliyun-oss|oss|r2|cloudflare_r2|cloudflare-r2|s3|aws_s3|aws-s3|custom|custom_s3|custom-s3)
       return 1
       ;;
     *)