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/listings/presentation/controllers/listings.controller.ts

@@ -26,6 +26,8 @@ import { CurrentUser } from '@modules/auth/presentation/decorators/current-user.
 import { Roles } from '@modules/auth/presentation/decorators/roles.decorator';
 import { JwtAuthGuard } from '@modules/auth/presentation/guards/jwt-auth.guard';
 import { RolesGuard } from '@modules/auth/presentation/guards/roles.guard';
+import { QuotaGuard } from '@modules/subscriptions/presentation/guards/quota.guard';
+import { RequireQuota } from '@modules/subscriptions/presentation/decorators/require-quota.decorator';
 import { FileValidationPipe, type UploadedFile as ValidatedFile } from '@modules/shared/infrastructure/pipes/file-validation.pipe';
 import { CreateListingCommand } from '../../application/commands/create-listing/create-listing.command';
 import { type CreateListingResult } from '../../application/commands/create-listing/create-listing.handler';
@@ -55,7 +57,9 @@ export class ListingsController {
   @ApiResponse({ status: 201, description: 'Listing created successfully' })
   @ApiResponse({ status: 400, description: 'Validation error' })
   @ApiResponse({ status: 401, description: 'Unauthorized' })
-  @UseGuards(JwtAuthGuard)
+  @ApiResponse({ status: 403, description: 'Quota exceeded' })
+  @UseGuards(JwtAuthGuard, QuotaGuard)
+  @RequireQuota('listings_created')
   @Post()
   async createListing(
     @Body() dto: CreateListingDto,