补充 VP 模块注册 + 前端 API 封装

- app.module.ts: 注册 VirtualPaymentModule
- config.ts + api.ts: 添加虚拟支付 API 端点
- useGravityPurchase.ts: VP 购买逻辑
- interview.vue / user.vue: 适配 VP 调用
- admin.controller.ts: 管理端虚拟支付相关调整
- payment.controller.spec.ts: 测试适配

zhiyin-app/src/config.ts

@@ -122,6 +122,10 @@ export const API_ENDPOINTS = {
     CHAT: '/career-advice/chat',
     POSITIONS: '/career-advice/positions',
   },
+  VIRTUAL_PAYMENT: {
+    CREATE: '/virtual-payment/create',
+    CHECK: (outTradeNo: string) => `/virtual-payment/check/${outTradeNo}`,
+  },
 } as const
 
 const PROD_API_HOST = import.meta.env.VITE_PROD_API_HOST || 'https://zhiyinwx.yzrcloud.cn'