fix: add status guards to prevent data loss

- create: auto-delete REJECTED→throw error; add tenantId filter
- remove: forbid PUBLISHED bank deletion
- removeItem: forbid PUBLISHED item deletion
- generateQuestions: restrict to DRAFT status only
- frontend: render MULTIPLE_CHOICE options/judgment/followupHints
- frontend: add judgment and followupHints to QuestionBankItem type
- add 12 service guard tests (109 total)

server/src/assessment/services/question-bank.service.ts

@@ -266,13 +266,11 @@ export class QuestionBankService {
     }
     if (createDto.templateId) {
       const existing = await this.bankRepository.findOne({
-        where: { templateId: createDto.templateId },
+        where: { templateId: createDto.templateId, tenantId: tenantId || undefined as any },
       });
       if (existing) {
-        if (existing.status === QuestionBankStatus.DRAFT || existing.status === QuestionBankStatus.REJECTED) {
-          await this.bankRepository.remove(existing);
-        } else {
-          throw new BadRequestException('该模板已关联有效题库，请编辑已有题库');
+        if (existing.status === QuestionBankStatus.DRAFT || existing.status === QuestionBankStatus.REJECTED || existing.status === QuestionBankStatus.PUBLISHED) {
+          throw new BadRequestException('该模板已关联题库，请编辑已有题库或删除后重建');
         }
       }
     }
@@ -349,6 +347,9 @@ export class QuestionBankService {
 
   async remove(id: string): Promise<void> {
     const bank = await this.findOne(id);
+    if (bank.status === QuestionBankStatus.PUBLISHED) {
+      throw new ForbiddenException('已发布的题库不可删除');
+    }
     await this.bankRepository.remove(bank);
   }
 
@@ -441,6 +442,9 @@ export class QuestionBankService {
     if (!item) {
       throw new NotFoundException(`QuestionBankItem with ID "${itemId}" not found`);
     }
+    if (item.status === QuestionBankItemStatus.PUBLISHED) {
+      throw new ForbiddenException('已发布的题目不可删除');
+    }
     await this.itemRepository.remove(item);
   }
 
@@ -452,6 +456,10 @@ export class QuestionBankService {
   ): Promise<QuestionBankItem[]> {
     const bank = await this.findOne(bankId);
 
+    if (bank.status !== QuestionBankStatus.DRAFT) {
+      throw new ForbiddenException('仅草稿状态的题库可生成题目');
+    }
+
     if (count <= 0 || count > 50) {
       throw new BadRequestException('生成数量必须在 1-50 之间');
     }