fix: auto-aggregate AI costs hourly instead of manual-only

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/modules/admin-costs/cost-aggregation.service.ts

@@ -1,12 +1,24 @@
-import { Injectable, Logger } from '@nestjs/common';
+import { Injectable, Logger, OnModuleInit, OnModuleDestroy } from '@nestjs/common';
 import { PrismaService } from '../../infrastructure/database/prisma.service';
 
+const AGGREGATE_INTERVAL_MS = 60 * 60 * 1000; // hourly
+
 @Injectable()
-export class CostAggregationService {
+export class CostAggregationService implements OnModuleInit, OnModuleDestroy {
   private readonly logger = new Logger(CostAggregationService.name);
+  private timer: ReturnType<typeof setInterval> | null = null;
 
   constructor(private readonly prisma: PrismaService) {}
 
+  async onModuleInit() {
+    await this.aggregateToday();
+    this.timer = setInterval(() => this.aggregateToday(), AGGREGATE_INTERVAL_MS);
+  }
+
+  onModuleDestroy() {
+    if (this.timer) clearInterval(this.timer);
+  }
+
   /** Aggregate today's AiUsageLog into CostDailySummary */
   async aggregateToday(): Promise<void> {
     const today = new Date(); today.setHours(0, 0, 0, 0);