Feat: Add newsletter subscription endpoint

functions/api/subscribe.js

@@ -0,0 +1,15 @@
+export async function onRequestPost(ctx) {
+  const { request, env } = ctx;
+  const { email } = await request.json().catch(() => ({}));
+  if (!email || !/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email)) {
+    return new Response(JSON.stringify({ error: 'Invalid email' }), { status: 400, headers: { 'Content-Type': 'application/json' } });
+  }
+  const cf = request.cf || {};
+  const geo = [cf.city, cf.region, cf.country].filter(Boolean).join(', ') || 'Unknown';
+  await fetch(`https://ntfy.sh/${env.NTFY_TOPIC}`, {
+    method: 'POST',
+    headers: { Priority: '3', Title: `New sub: ${geo}` },
+    body: email
+  });
+  return new Response(JSON.stringify({ ok: true }), { headers: { 'Content-Type': 'application/json' } });
+}