Feat: Add unsubscribe API endpoint

functions/api/unsubscribe.js

@@ -0,0 +1,13 @@
+export async function onRequestPost({ request, env }) {
+  const { email } = await request.json().catch(() => ({}));
+  if (!email || !/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email))
+    return new Response('{"error":"Invalid email"}', { status: 400, headers: { 'Content-Type': 'application/json' } });
+
+  await fetch(`https://ntfy.sh/${env.NTFY_TOPIC}`, {
+    method: 'POST',
+    headers: { Priority: '3', Title: `🔕 Unsubscribe` },
+    body: email
+  });
+  
+  return new Response('{"ok":true}', { headers: { 'Content-Type': 'application/json' } });
+}