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/k3s/README.md

@@ -11,6 +11,7 @@
 
 - `provider: minio` 或 `provider: mino`：部署 MinIO 和 `minio-init`
 - `provider: aliyun` / `aliyun_oss` / `aliyun-oss` / `oss`：使用 `deploy/k3s-aliyun-oss` overlay，不部署 MinIO 和 `minio-init`
+- `provider: r2` / `s3` / `custom_s3`：复用 S3 兼容客户端，不部署自建 MinIO；Cloudflare R2 建议配置 `region: auto` 和 `force_path_style: true`
 
 ## 1. 准备镜像