feat(admin): 添加账号批量调度开关功能

- 后端：支持批量更新账号的 schedulable 字段
  - 在 BulkUpdateAccountsRequest 中添加 schedulable 参数
  - 在 AccountBulkUpdate 中添加 schedulable 字段支持
  - 更新 repository 层批量更新 SQL 逻辑
- 前端：在账号管理页面添加批量调度控制
  - 新增"批量启用调度"和"批量停止调度"按钮
  - 添加 handleBulkToggleSchedulable 处理函数
  - 显示具体的成功提示信息（包含操作账号数量）
- 国际化：添加批量调度相关中英文翻译
- 优化：添加 search 参数标准化和验证（account_handler）

frontend/src/i18n/locales/en.ts

@@ -1076,12 +1076,16 @@ export default {
       tokenRefreshed: 'Token refreshed successfully',
       accountDeleted: 'Account deleted successfully',
       rateLimitCleared: 'Rate limit cleared successfully',
+      bulkSchedulableEnabled: 'Successfully enabled scheduling for {count} account(s)',
+      bulkSchedulableDisabled: 'Successfully disabled scheduling for {count} account(s)',
       bulkActions: {
         selected: '{count} account(s) selected',
         selectCurrentPage: 'Select this page',
         clear: 'Clear selection',
         edit: 'Bulk Edit',
-        delete: 'Bulk Delete'
+        delete: 'Bulk Delete',
+        enableScheduling: 'Enable Scheduling',
+        disableScheduling: 'Disable Scheduling'
       },
       bulkEdit: {
         title: 'Bulk Edit Accounts',

frontend/src/i18n/locales/zh.ts

@@ -1212,12 +1212,16 @@ export default {
       accountCreatedSuccess: '账号添加成功',
       accountUpdatedSuccess: '账号更新成功',
       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',
       bulkActions: {
         selected: '已选择 {count} 个账号',
         selectCurrentPage: '本页全选',
         clear: '清除选择',
         edit: '批量编辑账号',
-        delete: '批量删除'
+        delete: '批量删除',
+        enableScheduling: '批量启用调度',
+        disableScheduling: '批量停止调度'
       },
       bulkEdit: {
         title: '批量编辑账号',