feat(i18n): restrict public routes and metadata to enabled locales

- Add ENABLED_LOCALES configuration in i18n/links.js (currently ["pt"])
- Redirect inactive locale prefixes to /pt via 307 in middleware.js
- Restrict root locale negotiation to active locales with fallback to pt
- Hide LanguageSelector when only one locale is enabled
- Generate sitemap, hreflang alternates, and og:locale only for active locales
- Generate static SSG pages only for active locales in build
- Adapt check:i18n and smoke-imagem.sh to validate active vs inactive locales

Co-Authored-By: Antigravity <noreply@google.com>

app/[locale]/layout.jsx

@@ -3,6 +3,7 @@ import { JetBrains_Mono, Manrope, Space_Grotesk } from "next/font/google";
 import { NextIntlClientProvider } from "next-intl";
 import { getMessages } from "next-intl/server";
 import { routing } from "@/i18n/routing";
+import { ENABLED_LOCALES } from "@/i18n/links";
 import "../globals.css";
 import Providers from "@/components/Providers";
 import { SITE, jsonLd } from "@/lib/seo";
@@ -38,7 +39,7 @@ const LANG_MAP = {
 };
 
 export function generateStaticParams() {
-	return routing.locales.map((locale) => ({ locale }));
+	return ENABLED_LOCALES.map((locale) => ({ locale }));
 }
 
 export async function generateMetadata({ params }) {
@@ -52,6 +53,8 @@ export async function generateMetadata({ params }) {
 		"zh-CN": "zh_CN",
 	};
 
+	const alternateLocales = ENABLED_LOCALES.filter((l) => l !== locale).map((l) => ogLocaleMap[l]);
+
 	return {
 		metadataBase: new URL(SITE.url),
 		title: {
@@ -71,10 +74,16 @@ export async function generateMetadata({ params }) {
 			"comparar ESP32", "qual ESP32 escolher", "datasheet ESP32",
 			"microcontrolador", "Espressif", "ESP-IDF", "IoT", "sistemas embarcados",
 		],
-		alternates: { canonical: `/${locale}` },
+		alternates: {
+			canonical: `/${locale}`,
+			languages: Object.fromEntries(
+				ENABLED_LOCALES.map((l) => [LANG_MAP[l] || l, `/${l}`])
+			),
+		},
 		openGraph: {
 			type: "website",
 			locale: ogLocaleMap[locale] || "pt_BR",
+			alternateLocale: alternateLocales.length > 0 ? alternateLocales : undefined,
 			url: `${SITE.url}/${locale}`,
 			siteName: SITE.nome,
 			title: "ESPDocs · Documentação do ESP32 em português",
@@ -127,7 +136,7 @@ export const viewport = {
 
 export default async function RootLayout({ children, params }) {
 	const { locale } = await params;
-	if (!routing.locales.includes(locale)) {
+	if (!ENABLED_LOCALES.includes(locale)) {
 		notFound();
 	}