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/events/[id]/page.tsx

@@ -2,6 +2,7 @@ import type { Metadata } from "next";
 import EventDetailClient from "./EventDetailClient";
 import { EventJsonLd, BreadcrumbJsonLd } from "@/components/public/JsonLd";
 import { apiUrl } from "@/lib/api-base";
+import { getMeetupStartUtc, getMeetupEndUtc } from "@/lib/meetupEventTime";
 
 async function fetchEvent(id: string) {
   try {
@@ -59,6 +60,15 @@ export default async function EventDetailPage({ params }: Props) {
   const event = await fetchEvent(id);
   const siteUrl = process.env.NEXT_PUBLIC_SITE_URL || "https://belgianbitcoinembassy.org";
 
+  let startDate = event?.date;
+  let endDate: string | undefined;
+  if (event?.date) {
+    const start = getMeetupStartUtc(event.date, event.time || "00:00");
+    if (!Number.isNaN(start.getTime())) startDate = start.toISOString();
+    const end = getMeetupEndUtc(event.date, event.time || "");
+    if (end && !Number.isNaN(end.getTime())) endDate = end.toISOString();
+  }
+
   return (
     <>
       {event && (
@@ -66,7 +76,8 @@ export default async function EventDetailPage({ params }: Props) {
           <EventJsonLd
             name={event.title}
             description={event.description}
-            startDate={event.date}
+            startDate={startDate}
+            endDate={endDate}
             location={event.location}
             url={`${siteUrl}/events/${id}`}
             imageUrl={event.imageId ? `${siteUrl}/media/${event.imageId}` : undefined}