feat(i18n): English localization (phase 3)

- Translate content to English across messages/en.json, data/en, lib/data/en, and public/exemplos/en
- Implement localized routing, slugs, and language negotiation with fallback to en
- Build dedicated search index for English with strict book exclusion
- Update components and pages to dynamically render localized strings and datasets
- Verify full structural parity and exact 1:1 match on Portuguese pages via comparator

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

middleware.js

@@ -1,7 +1,7 @@
 import createMiddleware from "next-intl/middleware";
 import { NextResponse } from "next/server";
 import { routing } from "./i18n/routing";
-import { ALL_LOCALE_CODES, ENABLED_LOCALES, getPtPath } from "./i18n/links";
+import { ALL_LOCALE_CODES, ENABLED_LOCALES, getLocalizedHref } from "./i18n/links";
 
 const intlMiddleware = createMiddleware(routing);
 
@@ -76,18 +76,20 @@ export default function middleware(request) {
 		return response;
 	}
 
-	// 2. Idiomas INATIVOS: prefixos (/en, /es, /fr, /de, /zh-CN e qualquer subcaminho)
-	// Redirecionam com 307 para o mesmo caminho em /pt quando o slug existir lá; se não souber mapear o slug, para /pt.
-	// O 404 do livro fora de pt não se aplica a inativos (redirecionam para /pt/livro aqui).
+	// 2. Idiomas INATIVOS: prefixos (/es, /fr, /de, /zh-CN etc.)
+	// Redirecionam com 307 para o mesmo caminho no idioma fallback (en se ativo, senão pt) quando o slug existir lá.
 	const inactiveLocales = ALL_LOCALE_CODES.filter((l) => !ENABLED_LOCALES.includes(l));
 	if (inactiveLocales.length > 0) {
 		const isInactive = inactiveLocales.some(
 			(loc) => pathname === `/${loc}` || pathname.startsWith(`/${loc}/`)
 		);
 		if (isInactive) {
-			const targetPath = getPtPath(pathname);
+			const fallbackLocale = ENABLED_LOCALES.includes("en") ? "en" : "pt";
+			const targetPath = getLocalizedHref(pathname, fallbackLocale);
 			const url = new URL(targetPath, request.url);
-			url.search = search;
+			if (search && !targetPath.includes("?")) {
+				url.search = search;
+			}
 			return NextResponse.redirect(url, 307);
 		}
 	}