fix: 全部TS错误修复(25->0) + 证书API 500修复 + i18n缺失key补全 + 类型定义修正

- 证书API 500修复: AssessmentCertificate实体注册到app.module.ts
- 前端TS错误25个清零: i18n key 17个, 类型定义8个
- i18n补全: 17个缺失key添加到zh/en/ja
- KnowledgeFile类型: 添加title, content字段
- importService: 改用apiClient.request替代raw fetch
- ModeSelector: 移除jsx prop
- questionBankService: .ok -> .status >= 400
- NotebookDetailView: .filter -> .items.filter
- ImportTasksDrawer: tasks.items提取
- API端点审计: 16/16通过
- 数据库Schema审计: 25表288列一致
- AGENTS.md更新

web/components/drawers/ImportTasksDrawer.tsx

@@ -29,7 +29,8 @@ export const ImportTasksDrawer: React.FC<ImportTasksDrawerProps> = ({
                 importService.getAll(authToken),
                 knowledgeGroupService.getGroups()
             ]);
-            setImportTasks(tasks);
+            const taskItems = 'items' in tasks ? tasks.items : tasks;
+            setImportTasks(taskItems);
 
             // Flatten the groups tree so we can easily find names by ID
             const flat: KnowledgeGroup[] = [];