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/lib/seo.ts

@@ -0,0 +1,38 @@
+import { apiUrl } from "./api-base";
+
+/**
+ * Server-side fetch of the public site settings (social links, titles, …).
+ * Cached/revalidated so it doesn't hit the backend on every render.
+ */
+export async function fetchPublicSettings(): Promise<Record<string, string>> {
+  try {
+    const res = await fetch(apiUrl("/settings/public"), {
+      next: { revalidate: 3600 },
+    });
+    if (!res.ok) return {};
+    return (await res.json()) as Record<string, string>;
+  } catch {
+    return {};
+  }
+}
+
+/** Setting keys that hold a public social/profile URL, in display order. */
+const SOCIAL_SETTING_KEYS = [
+  "telegram_link",
+  "nostr_link",
+  "x_link",
+  "youtube_link",
+  "discord_link",
+  "linkedin_link",
+] as const;
+
+/**
+ * Build the list of real social URLs for schema.org `sameAs` from settings.
+ * Only includes entries that are actually configured (non-empty, http(s)).
+ */
+export function socialUrlsFromSettings(
+  settings: Record<string, string>,
+): string[] {
+  return SOCIAL_SETTING_KEYS.map((key) => settings[key]?.trim())
+    .filter((url): url is string => !!url && /^https?:\/\//i.test(url));
+}