feat(admin): 添加提示词批量删除和定时同步功能

- 后端新增批量删除提示词接口和实现
- 前端管理页面添加多选和批量删除功能
- 添加定时同步GitHub远程提示词源功能
- 新增系统设置中的提示词同步配置选项
- 更新文档说明新的批量操作和定时同步功能
- 添加相关的测试用例和依赖库

service/settings.go

@@ -32,6 +32,9 @@ func SaveSettings(settings model.Settings) (model.Settings, error) {
 	settings = normalizeSettings(settings)
 	keepPrivateAPIKeys(&settings, normalizeSettings(saved))
 	result, err := repository.SaveSettings(settings, now())
+	if err == nil {
+		RefreshPromptSyncScheduler()
+	}
 	return hidePrivateAPIKeys(result), err
 }
 
@@ -72,6 +75,7 @@ func normalizePrivateSetting(setting model.PrivateSetting) model.PrivateSetting
 	if setting.Channels == nil {
 		setting.Channels = []model.ModelChannel{}
 	}
+	setting.PromptSync = normalizePromptSyncSetting(setting.PromptSync)
 	for i := range setting.Channels {
 		if setting.Channels[i].Protocol == "" {
 			setting.Channels[i].Protocol = "openai"