fix: prevent hourly API crash from unhandled CostAggregationService rejection

- setInterval callback lacked .catch() — unhandled Promise rejection
  crashed the Node.js process exactly 1 hour after startup
- AiUsageLog table missing in current DB → aggregateToday() rejects →
  process.exit(1) in Node 22

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

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

@@ -16,7 +16,7 @@ export class CostAggregationService implements OnModuleInit, OnModuleDestroy {
     } catch (err: any) {
       this.logger.warn(`Initial cost aggregation failed: ${err.message}`);
     }
-    this.timer = setInterval(() => this.aggregateToday(), AGGREGATE_INTERVAL_MS);
+    this.timer = setInterval(() => this.aggregateToday().catch(err => this.logger.warn(`Hourly cost aggregation failed: ${err.message}`)), AGGREGATE_INTERVAL_MS);
   }
 
   onModuleDestroy() {