fix(admin): copy buttons dead on HTTP origin — execCommand fallback

navigator.clipboard 仅安全上下文（HTTPS/localhost）可用，测试服务器经
http://IP:32005 访问时为 undefined，四处复制按钮（公开令牌/分享链接/
嵌入代码/重置密码）点击即抛 TypeError 且无提示。统一 utils/clipboard
copyText：API 优先、失败降级隐藏 textarea + execCommand。

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

apps/admin/src/components/business/albums/AlbumSummaryHeader.vue

@@ -125,6 +125,7 @@
   } from '@element-plus/icons-vue'
   import { ElMessage } from 'element-plus'
   import { formatDateTime } from '@/utils/albums/format'
+  import { copyText } from '@/utils/clipboard'
 
   defineOptions({ name: 'AlbumSummaryHeader' })
 
@@ -163,8 +164,11 @@
   ])
 
   async function copyToken() {
-    await navigator.clipboard.writeText(props.album.publicToken)
-    ElMessage.success(t('albumsManage.list.copied'))
+    if (await copyText(props.album.publicToken)) {
+      ElMessage.success(t('albumsManage.list.copied'))
+    } else {
+      ElMessage.error(t('setting.actions.copyFailed'))
+    }
   }
 </script>