feat(cms): implement multi-language support across frontend and admin UI

apps/backend/src/routes/articles.ts

@@ -108,4 +108,50 @@ export const articlesRoute = new Elysia({ prefix: "/articles" })
       set.status = 500;
       return { error: "Failed to delete article" };
     }
+  })
+  .patch("/:id/translations", async ({ params, body, set }) => {
+    const id = Number(params.id);
+    if (isNaN(id)) {
+      set.status = 400;
+      return { error: "Invalid article ID" };
+    }
+
+    const payload = body as any;
+    const results: any[] = [];
+    const LANGS = ['th', 'en', 'ja', 'zh', 'vi', 'ko'];
+
+    for (const lang of LANGS) {
+      const title = typeof payload.title === 'string' ? (lang === 'th' ? payload.title : null) : payload.title?.[lang];
+      const content = typeof payload.content === 'string' ? (lang === 'th' ? payload.content : null) : payload.content?.[lang];
+
+      if (!title && !content) continue;
+
+      const existing = await prisma.articleTranslation.findUnique({
+        where: { articleId_langCode: { articleId: id, langCode: lang } }
+      });
+
+      const updateData: any = {};
+      if (title) updateData.title = title;
+      if (content) updateData.content = content;
+
+      if (existing) {
+        const updated = await prisma.articleTranslation.update({
+          where: { id: existing.id },
+          data: updateData
+        });
+        results.push(updated);
+      } else {
+        const created = await prisma.articleTranslation.create({
+          data: { articleId: id, langCode: lang, ...updateData }
+        });
+        results.push(created);
+      }
+    }
+
+    const updated = await prisma.article.findUnique({
+      where: { id },
+      include: { translations: true }
+    });
+
+    return { success: true, translations: results, article: updated };
   });