feat: AI岗位专区 — 5个AI岗位置顶 + 首页分组展示

- schema: HotPosition 新增 category 字段 (ai/traditional)
- positions: 5 AI岗位 (AI算法/大模型应用/Prompt/AI产品/AI运维) + 7传统岗位
- frontend: 首页拆分 "🔥 AI热门岗位" 置顶高亮 + "更多岗位" 折叠
- ai服务: 新增 primaryFallbackModel (sensenova-6.7-flash-lite) 降级链路

backend/src/modules/ai/ai.service.ts

@@ -1,6 +1,6 @@
-import { Injectable, Logger } from '@nestjs/common'
-import axios from 'axios'
-import https from 'https'
+import { Injectable, Logger } from "@nestjs/common"
+import axios from "axios"
+import https from "https"
 
 interface AiCallOptions {
   systemPrompt: string
@@ -15,26 +15,35 @@ const httpAgent = new https.Agent({ rejectUnauthorized: true, keepAlive: true })
 export class AiService {
   private readonly logger = new Logger(AiService.name)
 
-  private readonly primaryUrl = process.env.AI_PRIMARY_URL || 'https://token.sensenova.cn/v1'
-  private readonly primaryKey = process.env.AI_PRIMARY_KEY || ''
-  private readonly primaryModel = process.env.AI_PRIMARY_MODEL || 'deepseek-v4-flash'
+  private readonly primaryUrl = process.env.AI_PRIMARY_URL || "https://token.sensenova.cn/v1"
+  private readonly primaryKey = process.env.AI_PRIMARY_KEY || ""
+  private readonly primaryModel = process.env.AI_PRIMARY_MODEL || "deepseek-v4-flash"
+  private readonly primaryFallbackModel = process.env.AI_PRIMARY_FALLBACK_MODEL || "sensenova-6.7-flash-lite"
 
-  private readonly backupUrl = process.env.AI_BACKUP_URL || 'https://integrate.api.nvidia.com/v1'
-  private readonly backupKey = process.env.AI_BACKUP_KEY || ''
-  private readonly backupModel = process.env.AI_BACKUP_MODEL || 'stepfun-ai/step-3.5-flash'
+  private readonly backupUrl = process.env.AI_BACKUP_URL || "https://integrate.api.nvidia.com/v1"
+  private readonly backupKey = process.env.AI_BACKUP_KEY || ""
+  private readonly backupModel = process.env.AI_BACKUP_MODEL || "stepfun-ai/step-3.5-flash"
 
   async call(options: AiCallOptions): Promise<string> {
     const { systemPrompt, userMessage, temperature = 0.7, maxTokens = 2048 } = options
 
-    // Try primary AI
+    // Try primary AI (deepseek-v4-flash on sensenova)
     try {
       const result = await this.callApi(this.primaryUrl, this.primaryKey, this.primaryModel, systemPrompt, userMessage, temperature, maxTokens)
       if (result) return result
     } catch (e) {
-      this.logger.warn(`Primary AI failed: ${(e as Error).message}, trying backup...`)
+      this.logger.warn(`Primary AI failed: ${(e as Error).message}, trying primary fallback...`)
     }
 
-    // Try backup AI
+    // Try primary fallback model (sensenova-6.7-flash-lite, same provider)
+    try {
+      const result = await this.callApi(this.primaryUrl, this.primaryKey, this.primaryFallbackModel, systemPrompt, userMessage, temperature, maxTokens)
+      if (result) return result
+    } catch (e) {
+      this.logger.warn(`Primary fallback AI also failed: ${(e as Error).message}, trying backup...`)
+    }
+
+    // Try backup AI (NVIDIA)
     try {
       const result = await this.callApi(this.backupUrl, this.backupKey, this.backupModel, systemPrompt, userMessage, temperature, maxTokens)
       if (result) return result
@@ -43,7 +52,7 @@ export class AiService {
     }
 
     // Final fallback
-    throw new Error('AI 服务暂时不可用，请稍后重试')
+    throw new Error("AI \u670d\u52a1\u6682\u65f6\u4e0d\u53ef\u7528\uff0c\u8bf7\u7a0d\u540e\u91cd\u8bd5")
   }
 
   private async callApi(
@@ -56,16 +65,16 @@ export class AiService {
       {
         model,
         messages: [
-          { role: 'system', content: systemPrompt },
-          { role: 'user', content: userMessage },
+          { role: "system", content: systemPrompt },
+          { role: "user", content: userMessage },
         ],
         temperature,
         max_tokens: maxTokens,
       },
       {
         headers: {
-          'Authorization': `Bearer ${apiKey}`,
-          'Content-Type': 'application/json',
+          "Authorization": `Bearer ${apiKey}`,
+          "Content-Type": "application/json",
         },
         timeout: 60000,
         httpsAgent: httpAgent,

backend/src/modules/positions/positions.schema.ts

@@ -1,20 +1,22 @@
-import { Prop, Schema, SchemaFactory } from '@nestjs/mongoose'
-import { Document } from 'mongoose'
+import { Prop, Schema, SchemaFactory } from "@nestjs/mongoose"
+import { Document } from "mongoose"
 
 export type HotPositionDocument = HotPosition & Document
 
+export type PositionCategory = "ai" | "traditional"
+
 @Schema({ timestamps: true })
 export class HotPosition {
   @Prop({ required: true })
   name: string
 
-  @Prop({ default: '' })
+  @Prop({ default: "" })
   salary?: string
 
-  @Prop({ default: '' })
+  @Prop({ default: "" })
   company?: string
 
-  @Prop({ default: '' })
+  @Prop({ default: "" })
   icon?: string
 
   @Prop({ default: 0 })
@@ -22,7 +24,11 @@ export class HotPosition {
 
   @Prop({ default: true })
   active: boolean
+
+  @Prop({ type: String, enum: ["ai", "traditional"], default: "traditional" })
+  category: PositionCategory
 }
 
 export const HotPositionSchema = SchemaFactory.createForClass(HotPosition)
 HotPositionSchema.index({ sort: 1 })
+HotPositionSchema.index({ category: 1, active: 1 })