feat: improve dashboard refresh state

src/i18n/locales/en-US.ts

@@ -65,6 +65,9 @@ export default {
       yesterdayShares: 'Yesterday: {count}',
       serverUptime: 'Uptime',
       refresh: 'Refresh',
+      refreshing: 'Refreshing',
+      lastUpdated: 'Last updated: {time}',
+      loadFailed: 'Failed to load dashboard data',
       fileHealth: 'File Health',
       fileHealthDesc: 'Real file records grouped by availability, expiry, and type.',
       activeFileRatio: 'Active Ratio',

src/i18n/locales/zh-CN.ts

@@ -65,6 +65,9 @@ export default {
       yesterdayShares: '昨日分享：{count}',
       serverUptime: '运行时间',
       refresh: '刷新数据',
+      refreshing: '刷新中',
+      lastUpdated: '最近更新：{time}',
+      loadFailed: '仪表盘数据加载失败',
       fileHealth: '文件健康',
       fileHealthDesc: '基于真实文件记录统计有效、过期和类型分布。',
       activeFileRatio: '有效占比',