feat: serve well-known nostr.json via build-time fetch (#206)

Replace meta-refresh redirect with a static Astro endpoint that fetches
relay.dyne.org's nostr.json at build time, so curl and other non-browser
clients get real JSON instead of an HTML redirect page.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: puria

src/pages/.well-known/nostr.json.md

@@ -0,0 +1,17 @@
+import type { APIRoute } from 'astro';
+
+const UPSTREAM = 'https://relay.dyne.org/.well-known/nostr.json';
+
+export const GET: APIRoute = async () => {
+	const res = await fetch(UPSTREAM);
+	if (!res.ok) {
+		throw new Error(`Failed to fetch ${UPSTREAM}: ${res.status} ${res.statusText}`);
+	}
+	const body = await res.text();
+	return new Response(body, {
+		headers: {
+			'Content-Type': 'application/json; charset=utf-8',
+			'Access-Control-Allow-Origin': '*',
+		},
+	});
+};