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>

i18n/links.js

@@ -5,7 +5,7 @@
 
 // Ponto único de configuração de idiomas ATIVOS.
 // Para ativar um novo idioma no site, basta adicionar seu código aqui (ex.: ["pt", "en", "es"]).
-export const ENABLED_LOCALES = ["pt", "en", "es"];
+export const ENABLED_LOCALES = ["pt", "en", "es", "fr", "de"];
 
 export const ALL_LOCALES = [
 	{ code: "pt", label: "Português", short: "PT", lang: "pt-BR", og: "pt_BR" },