feat: internationalize API error responses by locale

Add shared error codes with zh/en/ms messages, coded app exceptions,
and locale-aware global filter. Frontends send X-Locale so error text
matches the active UI language.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/src/domains/operations/content/content.service.ts

@@ -1,9 +1,9 @@
 import {
   BadRequestException,
   Injectable,
-  NotFoundException,
 } from '@nestjs/common';
 import { PrismaService } from '../../../shared/prisma/prisma.service';
+import { appBadRequest, appNotFound } from '../../../shared/common/app-error';
 
 export const CONTENT_TYPES = ['BANNER', 'NOTICE', 'TICKER'] as const;
 export type ContentType = (typeof CONTENT_TYPES)[number];
@@ -50,21 +50,21 @@ export class ContentService {
 
   private assertContentType(type: string): ContentType {
     if (!CONTENT_TYPES.includes(type as ContentType)) {
-      throw new BadRequestException(`Invalid contentType: ${type}`);
+      throw appBadRequest('CONTENT_TYPE_INVALID', { type });
     }
     return type as ContentType;
   }
 
   private assertStatus(status: string): ContentStatus {
     if (!CONTENT_STATUSES.includes(status as ContentStatus)) {
-      throw new BadRequestException(`Invalid status: ${status}`);
+      throw appBadRequest('CONTENT_STATUS_INVALID', { status });
     }
     return status as ContentStatus;
   }
 
   private validateSchedule(startTime?: Date | null, endTime?: Date | null) {
     if (startTime && endTime && endTime <= startTime) {
-      throw new BadRequestException('endTime must be after startTime');
+      throw appBadRequest('CONTENT_END_BEFORE_START');
     }
   }
 
@@ -74,16 +74,16 @@ export class ContentService {
     status: ContentStatus,
   ) {
     if (!translations.length) {
-      throw new BadRequestException('At least one translation required');
+      throw appBadRequest('CONTENT_TRANSLATION_REQUIRED');
     }
 
     const locales = new Set<string>();
     for (const tr of translations) {
       if (!tr.locale?.trim()) {
-        throw new BadRequestException('Translation locale required');
+        throw appBadRequest('CONTENT_LOCALE_REQUIRED');
       }
       if (locales.has(tr.locale)) {
-        throw new BadRequestException(`Duplicate locale: ${tr.locale}`);
+        throw appBadRequest('CONTENT_LOCALE_DUPLICATE', { locale: tr.locale });
       }
       locales.add(tr.locale);
     }
@@ -101,12 +101,12 @@ export class ContentService {
     });
 
     if (!hasUsable) {
-      throw new BadRequestException(
+      throw appBadRequest(
         contentType === 'BANNER'
-          ? 'ACTIVE banner requires imageUrl in at least one locale'
+          ? 'CONTENT_ACTIVE_BANNER_INCOMPLETE'
           : contentType === 'NOTICE'
-            ? 'ACTIVE notice requires title or body in at least one locale'
-            : 'ACTIVE ticker requires body in at least one locale',
+            ? 'CONTENT_ACTIVE_NOTICE_INCOMPLETE'
+            : 'CONTENT_ACTIVE_TICKER_INCOMPLETE',
       );
     }
   }
@@ -114,10 +114,10 @@ export class ContentService {
   private validateLink(linkType?: string | null, linkTarget?: string | null) {
     if (!linkType) return;
     if (!CONTENT_LINK_TYPES.includes(linkType as ContentLinkType)) {
-      throw new BadRequestException(`Invalid linkType: ${linkType}`);
+      throw appBadRequest('CONTENT_LINK_TYPE_INVALID', { linkType });
     }
     if (!linkTarget?.trim()) {
-      throw new BadRequestException('linkTarget required when linkType is set');
+      throw appBadRequest('CONTENT_LINK_TARGET_REQUIRED');
     }
   }
 
@@ -197,7 +197,7 @@ export class ContentService {
       where: { id },
       include: { translations: true },
     });
-    if (!item) throw new NotFoundException('Content not found');
+    if (!item) throw appNotFound('CONTENT_NOT_FOUND');
     return item;
   }