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/notifications/notifications.module.ts

@@ -2,6 +2,7 @@ import { Module } from '@nestjs/common';
 import { CqrsModule } from '@nestjs/cqrs';
 import { SendNotificationHandler } from './application/commands/send-notification/send-notification.handler';
 import { AgentVerifiedListener } from './application/listeners/agent-verified.listener';
+import { QuotaExceededListener } from './application/listeners/quota-exceeded.listener';
 import { UserRegisteredListener } from './application/listeners/user-registered.listener';
 import { NOTIFICATION_PREFERENCE_REPOSITORY } from './domain/repositories/notification-preference.repository';
 import { NOTIFICATION_REPOSITORY } from './domain/repositories/notification.repository';
@@ -14,7 +15,7 @@ import { NotificationsController } from './presentation/controllers/notification
 
 const CommandHandlers = [SendNotificationHandler];
 
-const EventListeners = [UserRegisteredListener, AgentVerifiedListener];
+const EventListeners = [UserRegisteredListener, AgentVerifiedListener, QuotaExceededListener];
 
 @Module({
   imports: [CqrsModule],