feat(server): add booking, payment, and scheduler modules

Booking: reservation with atomic transactions, cancellation with refund
logic based on cancelHoursLimit (23 tests)
Payment: WeChat Pay integration (mock), order lifecycle, membership
creation on payment callback (13 tests)
Scheduler: cron tasks for slot generation, cleanup, membership expiry (8 tests)
109 total tests passing across 9 test suites

packages/server/src/payment/payment.module.ts

@@ -0,0 +1,13 @@
+import { Module } from '@nestjs/common'
+import { PrismaModule } from '../prisma/prisma.module'
+import { PaymentService } from './payment.service'
+import { PaymentController } from './payment.controller'
+import { WechatPayService } from './wechat-pay.service'
+
+@Module({
+  imports: [PrismaModule],
+  controllers: [PaymentController],
+  providers: [PaymentService, WechatPayService],
+  exports: [PaymentService],
+})
+export class PaymentModule {}