fix: interview creation show real error msg instead of generic failure

- Backend: wrap AI call in try/catch, throw HttpException(503)
  with msg 'AI 服务暂时不可用，请稍后重试'
- Backend: AllExceptionsFilter preserve original error message
  for non-HttpException errors
- Frontend: handle string/object res.data, show statusCode
  as fallback when message is unavailable

backend/src/modules/interview/interview.service.ts

@@ -1,4 +1,4 @@
-import { Injectable, HttpException, HttpStatus } from '@nestjs/common'
+import { Injectable, HttpException, HttpStatus, Logger } from '@nestjs/common'
 import { InjectModel } from '@nestjs/mongoose'
 import { Model } from 'mongoose'
 import { Interview, InterviewDocument } from './interview.schema'
@@ -11,6 +11,8 @@ import { analyzeSpeech } from '../../common/utils/filler-words'
 
 @Injectable()
 export class InterviewService {
+  private readonly logger = new Logger(InterviewService.name)
+
   constructor(
     @InjectModel(Interview.name) private interviewModel: Model<InterviewDocument>,
     @InjectModel(Progress.name) private progressModel: Model<ProgressDocument>,
@@ -25,11 +27,17 @@ export class InterviewService {
     const cost = await this.quotaService.checkInterview(userId)
 
     // Step 2: AI 生成第一个问题
-    const firstQuestion = await this.aiService.call({
-      systemPrompt: `你是一位专业的${position}面试官。请针对校招该岗位提出第一个面试问题，要求具体且有针对性。直接输出问题，不要多余内容。`,
-      userMessage: `请为${position}岗位的校招候选人提出第一个面试问题。`,
-      temperature: 0.8,
-    })
+    let firstQuestion: string
+    try {
+      firstQuestion = await this.aiService.call({
+        systemPrompt: `你是一位专业的${position}面试官。请针对校招该岗位提出第一个面试问题，要求具体且有针对性。直接输出问题，不要多余内容。`,
+        userMessage: `请为${position}岗位的校招候选人提出第一个面试问题。`,
+        temperature: 0.8,
+      })
+    } catch (e) {
+      this.logger.error(`AI call failed for interview create: ${(e as Error).message}`)
+      throw new HttpException('AI 服务暂时不可用，请稍后重试', HttpStatus.SERVICE_UNAVAILABLE)
+    }
 
     // Step 3: AI 调用成功后，扣除引力值并创建面试记录
     await this.quotaService.deductInterview(userId, cost)