feat(notifications): add ZaloOaLinkController + migration + schema — TEC-3065

Include files missed from previous commit:
- ZaloOaLinkController (GET /auth/zalo-oa/link, GET /auth/zalo-oa/callback, DELETE)
- prisma/schema.prisma — ZaloAccountLink model + User.zaloAccountLink relation
- prisma/migrations/20260421010000_add_zalo_account_links/migration.sql
- Updated ZaloOaService, webhook controller, notifications module, and specs

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

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

@@ -37,6 +37,7 @@ import { StringeeSmsService } from './infrastructure/services/stringee-sms.servi
 import { TemplateService } from './infrastructure/services/template.service';
 import { ZaloOaService } from './infrastructure/services/zalo-oa.service';
 import { NotificationsController } from './presentation/controllers/notifications.controller';
+import { ZaloOaLinkController } from './presentation/controllers/zalo-oa-link.controller';
 import { ZaloOaWebhookController } from './presentation/controllers/zalo-oa-webhook.controller';
 import { NotificationsGateway } from './presentation/gateways/notifications.gateway';
 
@@ -67,7 +68,7 @@ const EventListeners = [
 
 @Module({
   imports: [CqrsModule, AuthModule, MetricsModule],
-  controllers: [NotificationsController, ZaloOaWebhookController],
+  controllers: [NotificationsController, ZaloOaWebhookController, ZaloOaLinkController],
   providers: [
     // Repositories
     { provide: NOTIFICATION_REPOSITORY, useClass: PrismaNotificationRepository },