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>

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

@@ -0,0 +1,17 @@
+import { construirIndiceBusca } from "@/lib/searchIndex";
+
+export const dynamic = "force-static";
+
+export function generateStaticParams() {
+	return [{ locale: "pt" }, { locale: "en" }];
+}
+
+export async function GET(request, { params }) {
+	const { locale } = await params;
+	const loc = locale === "en" ? "en" : "pt";
+	return Response.json(construirIndiceBusca(loc), {
+		headers: {
+			"Cache-Control": "no-cache, no-store, must-revalidate",
+		},
+	});
+}