feat(public): merge secondary media gallery images with URL dedup

apps/api/src/public/public.service.ts

@@ -385,7 +385,7 @@ export class PublicService {
         designArea: detail?.designArea ?? null,
         pictureRequest: detail?.pictureRequest ?? null,
       },
-      media: (detail?.media as Record<string, unknown> | null) ?? null,
+      media: this.mergeMedia(detail, secondaryDetails),
       mediaByColor: this.groupImagesByColor(allVariants),
       options: this.mergeOptions(detail, secondaryDetails),
       sizeChart: this.mergeRowsByKey(detail, secondaryDetails, 'sizeChart'),
@@ -496,6 +496,35 @@ export class PublicService {
     return merged;
   }
 
+  /**
+   * Merge the gallery `media` across details: primary images first,
+   * secondary-only image URLs appended (URL-deduped). `primaryImageUrl`
+   * stays the primary's.
+   */
+  private mergeMedia(
+    primary: PublicGoodRow['originGood']['detail'],
+    secondaries: NonNullable<PublicGoodRow['originGood']['detail']>[],
+  ): Record<string, unknown> | null {
+    const toImages = (media: unknown): string[] => {
+      const images = (media as { images?: unknown } | null)?.images;
+      return Array.isArray(images) ? images.filter((u): u is string => typeof u === 'string') : [];
+    };
+    const primaryMedia = (primary?.media as Record<string, unknown> | null) ?? null;
+    if (!primaryMedia && secondaries.length === 0) return null;
+    const images = toImages(primaryMedia);
+    const seen = new Set(images);
+    for (const sec of secondaries) {
+      for (const url of toImages(sec.media)) {
+        if (!seen.has(url)) {
+          seen.add(url);
+          images.push(url);
+        }
+      }
+    }
+    if (images.length === 0) return null;
+    return { ...(primaryMedia ?? {}), images };
+  }
+
   private async buildTagGroupFilters(
     selectedGroups: PublicTagFilterDto[],
   ): Promise<Prisma.GoodWhereInput[]> {