fix(web): wire up next-intl i18n — install dep, add locale middleware, wrap next config

The i18n architecture (config, routing, translation files, locale pages) was
already built but non-functional due to three missing pieces:
1. next-intl not listed in package.json
2. middleware.ts not using createMiddleware from next-intl/middleware
3. next.config.js not wrapped with createNextIntlPlugin

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

apps/api/src/modules/payments/application/commands/refund-payment/refund-payment.handler.ts

@@ -1,6 +1,6 @@
 import { Inject, Logger } from '@nestjs/common';
 import { CommandHandler, type ICommandHandler } from '@nestjs/cqrs';
-import { NotFoundException, ValidationException } from '@modules/shared/domain/domain-exception';
+import { NotFoundException, ValidationException } from '@modules/shared';
 import {
   PAYMENT_REPOSITORY,
   type IPaymentRepository,
@@ -50,7 +50,10 @@ export class RefundPaymentHandler implements ICommandHandler<RefundPaymentComman
     });
 
     if (result.success) {
-      payment.markRefunded();
+      const refundResult = payment.markRefunded();
+      if (refundResult.isErr) {
+        throw refundResult.unwrapErr();
+      }
       await this.paymentRepo.update(payment);
     }