fix: import app config module in notifications module

Author: Arun-kushwaha007

apps/backend/src/notifications/notifications.module.ts

@@ -1,7 +1,9 @@
 import { Module } from '@nestjs/common';
+import { AppConfigModule } from '../config/app-config.module';
 import { NotificationsService } from './notifications.service';
 
 @Module({
+  imports: [AppConfigModule],
   providers: [NotificationsService],
   exports: [NotificationsService],
 })