feat: complete maintenance tracking backend

Service/Controller/Module:
- scheduleMaintenanceAsync: schedule work
- recordMaintenanceCost: log expenses
- getUpcomingMaintenance: due items
- getVehicleMaintenanceStats: cost aggregation

Endpoints:
- POST /maintenance/schedules
- POST /maintenance/costs
- PATCH /maintenance/schedules/:id
- GET /maintenance/upcoming/:vehicleId
- GET /maintenance/history/:vehicleId
- GET /maintenance/stats/:vehicleId

Migration: idempotent maintenance tables creation

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

apps/edr-freight-api/src/modules/maintenance/maintenance.module.ts

@@ -0,0 +1,15 @@
+import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
+import { MaintenanceSchedule } from './entities/maintenance-schedule.entity';
+import { MaintenanceCost } from './entities/maintenance-cost.entity';
+import { MaintenanceService } from './maintenance.service';
+import { MaintenanceRepository } from './maintenance.repository';
+import { MaintenanceController } from './maintenance.controller';
+
+@Module({
+  imports: [TypeOrmModule.forFeature([MaintenanceSchedule, MaintenanceCost])],
+  providers: [MaintenanceService, MaintenanceRepository],
+  controllers: [MaintenanceController],
+  exports: [MaintenanceService],
+})
+export class MaintenanceModule {}