feat: add SEO metadata, llms.txt, and markdown page mirrors

Centralize site metadata and social URLs for JSON-LD, expose llmstxt.org
content and per-page .md routes for LLM crawlers, and refactor blog/FAQ/events
pages with shared components.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/app/index.html.md/route.ts

@@ -0,0 +1,10 @@
+import { buildHomeMarkdown } from "@/lib/llms";
+
+export const revalidate = 300;
+
+export async function GET() {
+  const body = await buildHomeMarkdown();
+  return new Response(body, {
+    headers: { "Content-Type": "text/markdown; charset=utf-8" },
+  });
+}