feat(accounts): 自动刷新改为ETag增量同步并优化单账号更新体验

- 前端自动刷新改为 ETag/304 增量合并，减少全量重刷

- 单账号更新后增加静默窗口，避免刚更新即被自动刷新覆盖

- 列表筛选移除时改为待同步提示，不再立即触发全量补页

- 后端账号列表支持 If-None-Match，命中返回 304

- 单账号接口统一补充运行时容量字段并暴露 ETag 头

frontend/src/i18n/locales/en.ts

@@ -1280,6 +1280,8 @@ export default {
       refreshInterval15s: '15 seconds',
       refreshInterval30s: '30 seconds',
       autoRefreshCountdown: 'Auto refresh: {seconds}s',
+      listPendingSyncHint: 'List changes are pending sync. Click sync to load latest rows.',
+      listPendingSyncAction: 'Sync now',
       syncFromCrs: 'Sync from CRS',
       dataExport: 'Export',
       dataExportSelected: 'Export Selected',

frontend/src/i18n/locales/zh.ts

@@ -1368,6 +1368,8 @@ export default {
       refreshInterval15s: '15 秒',
       refreshInterval30s: '30 秒',
       autoRefreshCountdown: '自动刷新：{seconds}s',
+      listPendingSyncHint: '列表存在待同步变更，点击同步可补齐最新数据。',
+      listPendingSyncAction: '立即同步',
       syncFromCrs: '从 CRS 同步',
       dataExport: '导出',
       dataExportSelected: '导出选中',