feat(i18n): improve ai chat and settings localization

app/api/portal-clients/[clientId]/locale/route.ts

@@ -9,7 +9,7 @@ export async function PATCH(request: Request, { params }: { params: Promise<{ cl
   const actor = await getSessionContextFromHeaders(new Headers(request.headers));
 
   if (!actor) {
-    return NextResponse.json({ error: "Oturum gerekli." }, { status: 401 });
+    return NextResponse.json({ error: "clients.detail.portalLocaleUnauthenticated" }, { status: 401 });
   }
 
   try {
@@ -18,14 +18,25 @@ export async function PATCH(request: Request, { params }: { params: Promise<{ cl
     return NextResponse.json(result);
   } catch (error) {
     if (error instanceof SyntaxError) {
-      return NextResponse.json({ error: "Geçersiz JSON gövdesi." }, { status: 400 });
+      return NextResponse.json({ error: "clients.detail.invalidRequest" }, { status: 400 });
     }
     if (error instanceof PortalInvitationError) {
       const status = error.code === "FORBIDDEN" ? 403 : error.code === "CLIENT_NOT_FOUND" ? 404 : 400;
-      return NextResponse.json({ error: error.message, code: error.code }, { status });
+      return NextResponse.json({ error: portalLocaleErrorKey(error.code), code: error.code }, { status });
     }
 
     console.error("Client portal locale update failed", error);
-    return NextResponse.json({ error: "Portal dili güncellenemedi." }, { status: 500 });
+    return NextResponse.json({ error: "clients.detail.portalLocaleUpdateFailed" }, { status: 500 });
+  }
+}
+
+function portalLocaleErrorKey(code: PortalInvitationError["code"]) {
+  switch (code) {
+    case "FORBIDDEN":
+      return "clients.detail.portalLocaleForbidden";
+    case "CLIENT_NOT_FOUND":
+      return "clients.detail.portalLocaleClientNotFound";
+    default:
+      return "clients.detail.portalLocaleUpdateFailed";
   }
 }