feat(assets): album asset status — show current banner/cover/logo in admin branding tab

- 契约 listAlbumAssetStatus（GET /albums/{albumId}/assets）：每 (kind,locale)
  最新 effective 行 + 现签 URL；权限同详情（可见即读）；deleted → 404
- 服务端 AssetsService.status（createdAt,id DESC 组内取首；presignGet 现签）
- Admin 品牌资产页签改造：进入即加载现状——三种 kind 卡片（预览图/未设置
  空态/设置时间），banner 分全局/zh/en 槽位；上传成功自动刷新（替换语义）
- API 56/56、admin 87/87 + build 全绿

Co-Authored-By: Claude Code <noreply@anthropic.com>

apps/admin/src/locales/langs/en.json

@@ -407,7 +407,12 @@
       "stageError": "Upload failed",
       "reupload": "Upload Again",
       "preview": "Preview (signed URL, valid until {expiresAt})",
-      "invalidType": "Only jpg / png / heic images are supported"
+      "invalidType": "Only jpg / png / heic images are supported",
+      "statusHint": "Current effective banner / cover / logo (re-upload replaces)",
+      "refresh": "Refresh",
+      "notSet": "Not set",
+      "notSetHint": "Not uploaded yet; use the uploader below",
+      "setAt": "Set at {time}"
     },
     "members": {
       "title": "Album members",

apps/admin/src/locales/langs/zh.json

@@ -407,7 +407,12 @@
       "stageError": "上传失败",
       "reupload": "重新上传",
       "preview": "当前预览（签名 URL，{expiresAt} 前有效）",
-      "invalidType": "仅支持 jpg / png / heic 图片"
+      "invalidType": "仅支持 jpg / png / heic 图片",
+      "statusHint": "当前生效的宣传图 / 封面 / 标志（同类型再上传即替换）",
+      "refresh": "刷新",
+      "notSet": "未设置",
+      "notSetHint": "尚未上传，可选择下方上传",
+      "setAt": "设置于 {time}"
     },
     "members": {
       "title": "相册成员",