feat: implement KM-based maintenance scheduling

Add maintenance intervals configuration to track maintenance by kilometers
driven. When a maintenance is marked COMPLETED, automatically calculate and
schedule the next maintenance based on interval + current odometer reading.

Features:
- MaintenanceInterval entity: stores KM/day intervals per vehicle & type
- scheduleNextMaintenance(): creates next SCHEDULED item after completion
- nextDueKm field: tracks when next maintenance is due (in kilometers)
- getDueBoard() queries already support KM-based tracking

Maintenance now "marches forward" based on distance driven, not just dates.
Each vehicle type can have different intervals (e.g., oil every 10k km, tires 50k km).

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

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

@@ -4,7 +4,8 @@ import { Cron, CronExpression } from '@nestjs/schedule';
 import { NotificationAudience, NotificationType } from '@edr/types';
 import { DataSource, Repository } from 'typeorm';
 import { MaintenanceRepository } from './maintenance.repository';
-import { MaintenanceSchedule, MaintenanceStatus } from './entities/maintenance-schedule.entity';
+import { MaintenanceIntervalRepository } from './maintenance-interval.repository';
+import { MaintenanceSchedule, MaintenanceStatus, MaintenanceType } from './entities/maintenance-schedule.entity';
 import { MaintenanceCost } from './entities/maintenance-cost.entity';
 import { Vehicle, VehicleAvailability, VehicleStatus } from '../vehicles/entities/vehicle.entity';
 import { CreateMaintenanceScheduleDto, CreateMaintenanceCostDto, UpdateMaintenanceScheduleDto } from './dto/create-maintenance.dto';
@@ -16,6 +17,7 @@ export class MaintenanceService {
 
   constructor(
     private readonly maintenanceRepository: MaintenanceRepository,
+    private readonly intervalRepository: MaintenanceIntervalRepository,
     @InjectRepository(MaintenanceSchedule)
     private readonly scheduleRepository: Repository<MaintenanceSchedule>,
     @InjectRepository(MaintenanceCost)
@@ -119,6 +121,11 @@ export class MaintenanceService {
       ) {
         // Maintenance finished/aborted → vehicle back in service.
         await this.setVehicleMaintenanceState(updated.vehicleId, false);
+
+        // If completed, schedule the next maintenance based on interval
+        if (dto.status === MaintenanceStatus.COMPLETED && updated.odometerReading != null) {
+          await this.scheduleNextMaintenance(updated);
+        }
       } else if (dto.status === MaintenanceStatus.IN_PROGRESS) {
         // Maintenance started → keep the vehicle out of service.
         await this.setVehicleMaintenanceState(updated.vehicleId, true);
@@ -128,6 +135,60 @@ export class MaintenanceService {
     return updated!;
   }
 
+  private async scheduleNextMaintenance(completed: MaintenanceSchedule): Promise<void> {
+    try {
+      // Get maintenance interval for this type
+      const interval = await this.intervalRepository.getByVehicleAndType(
+        completed.vehicleId,
+        completed.maintenanceType as MaintenanceType,
+      );
+
+      if (!interval) return; // No interval defined, skip auto-scheduling
+
+      const now = new Date();
+      const completedKm = Number(completed.odometerReading ?? 0);
+
+      // Calculate next due based on KM interval
+      if (interval.intervalKm && interval.intervalKm > 0) {
+        const nextDueKm = completedKm + Number(interval.intervalKm);
+
+        // Create next scheduled maintenance
+        const nextSchedule = this.scheduleRepository.create({
+          vehicleId: completed.vehicleId,
+          maintenanceType: completed.maintenanceType,
+          description: `${interval.description || completed.description} (Next interval: ${nextDueKm} km)`,
+          scheduledDate: now,
+          nextDueKm,
+          status: MaintenanceStatus.SCHEDULED,
+        });
+        await this.scheduleRepository.save(nextSchedule);
+      }
+
+      // Calculate next due based on date interval
+      if (interval.intervalDays && interval.intervalDays > 0) {
+        const nextDueDate = new Date(now.getTime() + interval.intervalDays * 24 * 60 * 60 * 1000);
+
+        // If no KM-based next maintenance was created, use date-based
+        if (!interval.intervalKm) {
+          const nextSchedule = this.scheduleRepository.create({
+            vehicleId: completed.vehicleId,
+            maintenanceType: completed.maintenanceType,
+            description: completed.description,
+            scheduledDate: now,
+            nextDueDate,
+            status: MaintenanceStatus.SCHEDULED,
+          });
+          await this.scheduleRepository.save(nextSchedule);
+        }
+      }
+    } catch (err) {
+      this.logger.error(
+        `Failed to schedule next maintenance for vehicle ${completed.vehicleId}: ${(err as Error).message}`,
+        (err as Error).stack,
+      );
+    }
+  }
+
   async getUpcomingMaintenance(vehicleId: string) {
     return this.maintenanceRepository.getUpcomingMaintenance(vehicleId);
   }