feat(i18n): French and German localization (phase 5)

- Add full message catalogs and content for French (fr) and German (de)
- Implement ASCII canonical slugs for French and German routes
- Add language-specific search endpoints (/api/busca/fr, /api/busca/de)
- Configure strict 404 responses for /fr/livro and /de/livro
- Localize SEO, OpenGraph (fr_FR, de_DE), Twitter and JSON-LD schemas
- Add localized code example comments across 14 examples for fr and de
- Enable 'fr' and 'de' in ENABLED_LOCALES with root negotiation and redirect
- Extend test suite in check-i18n, smoke-imagem and verifica-vazamentos

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

app/api/busca/[locale]/route.js

@@ -3,12 +3,12 @@ import { construirIndiceBusca } from "@/lib/searchIndex";
 export const dynamic = "force-static";
 
 export function generateStaticParams() {
-	return [{ locale: "pt" }, { locale: "en" }, { locale: "es" }];
+	return [{ locale: "pt" }, { locale: "en" }, { locale: "es" }, { locale: "fr" }, { locale: "de" }];
 }
 
 export async function GET(request, { params }) {
 	const { locale } = await params;
-	const loc = locale === "en" ? "en" : locale === "es" ? "es" : "pt";
+	const loc = ["en", "es", "fr", "de"].includes(locale) ? locale : "pt";
 	return Response.json(construirIndiceBusca(loc), {
 		headers: {
 			"Cache-Control": "no-cache, no-store, must-revalidate",