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/scheduler/scheduler.module.ts

@@ -0,0 +1,13 @@
+import { Module } from '@nestjs/common'
+import { ScheduleModule } from '@nestjs/schedule'
+import { TimeSlotModule } from '../time-slot/time-slot.module'
+import { SchedulerService } from './scheduler.service'
+
+@Module({
+  imports: [
+    ScheduleModule.forRoot(),
+    TimeSlotModule,
+  ],
+  providers: [SchedulerService],
+})
+export class SchedulerModule {}