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/components/public/JsonLd.tsx

@@ -14,18 +14,21 @@ export function JsonLd({ data }: JsonLdProps) {
 const siteUrl =
   process.env.NEXT_PUBLIC_SITE_URL || "https://belgianbitcoinembassy.org";
 
-export function OrganizationJsonLd() {
+export function OrganizationJsonLd({ sameAs }: { sameAs?: string[] } = {}) {
+  const sameAsUrls =
+    sameAs && sameAs.length > 0 ? sameAs : ["https://t.me/belgianbitcoinembassy"];
   return (
     <JsonLd
       data={{
         "@context": "https://schema.org",
         "@type": "Organization",
+        "@id": `${siteUrl}/#organization`,
         name: "Belgian Bitcoin Embassy",
         url: siteUrl,
         logo: `${siteUrl}/og-default.png`,
         description:
           "Discover Bitcoin meetups across Belgium. Real conversations, education, and a strong local community.",
-        sameAs: ["https://t.me/belgianbitcoinembassy"],
+        sameAs: sameAsUrls,
         address: {
           "@type": "PostalAddress",
           addressLocality: "Antwerp",
@@ -103,6 +106,7 @@ interface EventJsonLdProps {
   name: string;
   description?: string;
   startDate: string;
+  endDate?: string;
   location?: string;
   url: string;
   imageUrl?: string;
@@ -114,6 +118,7 @@ export function EventJsonLd({
   name,
   description,
   startDate,
+  endDate,
   location,
   url,
   imageUrl,
@@ -130,6 +135,7 @@ export function EventJsonLd({
         name,
         description: description || `Bitcoin meetup: ${name}`,
         startDate,
+        ...(endDate ? { endDate } : {}),
         eventAttendanceMode: "https://schema.org/OfflineEventAttendanceMode",
         eventStatus: "https://schema.org/EventScheduled",
         ...(location