fix(账号管理): 调度批量结果明细与刷新优化

补充批量调度返回 success_ids/failed_ids 并增加合约/单测

前端加入降级处理与部分失败提示，表格行使用稳定 key

测试: make test-frontend

测试: go test ./internal/service -run BulkUpdateAccounts -tags=unit

测试: go test ./internal/server -run APIContracts -tags=unit

frontend/src/i18n/locales/en.ts

@@ -1105,6 +1105,8 @@ export default {
       rateLimitCleared: 'Rate limit cleared successfully',
       bulkSchedulableEnabled: 'Successfully enabled scheduling for {count} account(s)',
       bulkSchedulableDisabled: 'Successfully disabled scheduling for {count} account(s)',
+      bulkSchedulablePartial: 'Scheduling updated partially: {success} succeeded, {failed} failed',
+      bulkSchedulableResultUnknown: 'Bulk scheduling result incomplete. Please retry or refresh.',
       bulkActions: {
         selected: '{count} account(s) selected',
         selectCurrentPage: 'Select this page',

frontend/src/i18n/locales/zh.ts

@@ -1241,6 +1241,8 @@ export default {
       accountDeletedSuccess: '账号删除成功',
       bulkSchedulableEnabled: '成功启用 {count} 个账号的调度',
       bulkSchedulableDisabled: '成功停止 {count} 个账号的调度',
+      bulkSchedulablePartial: '部分调度更新成功：成功 {success} 个，失败 {failed} 个',
+      bulkSchedulableResultUnknown: '批量调度结果不完整，请稍后重试或刷新列表',
       bulkActions: {
         selected: '已选择 {count} 个账号',
         selectCurrentPage: '本页全选',