feat(subscriptions): implement subscription quota enforcement

- Apply QuotaGuard + @RequireQuota to listing creation and analytics endpoints
- Add QuotaExceeded domain event emitted when quota is exceeded
- Create ListingCreatedUsageHandler to auto-meter usage on listing creation
- Create QuotaExceededListener to send email notifications on quota exceeded
- Add maxAnalyticsQueries and maxMediaUploads fields to Plan model
- Add quota.exceeded email notification template
- Define quota limits per plan tier in seed data
- Add 15 unit tests covering guard, event handler, listener, and event

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/modules/subscriptions/subscriptions.module.ts

@@ -9,6 +9,7 @@ import { GetBillingHistoryHandler } from './application/queries/get-billing-hist
 import { GetPlanHandler } from './application/queries/get-plan/get-plan.handler';
 import { SUBSCRIPTION_REPOSITORY } from './domain/repositories/subscription.repository';
 import { PrismaSubscriptionRepository } from './infrastructure/repositories/prisma-subscription.repository';
+import { ListingCreatedUsageHandler } from './infrastructure/event-handlers/listing-created-usage.handler';
 import { SubscriptionsController } from './presentation/controllers/subscriptions.controller';
 import { QuotaGuard } from './presentation/guards/quota.guard';
 
@@ -35,6 +36,9 @@ const QueryHandlers = [
     // Guards
     QuotaGuard,
 
+    // Event Listeners
+    ListingCreatedUsageHandler,
+
     // CQRS
     ...CommandHandlers,
     ...QueryHandlers,