Add OPEN_REGISTRATION gate, signup request form, favicon

ui/lib/turnstile.ts

@@ -0,0 +1,19 @@
+export async function verifyTurnstile(token: string) {
+  const secretKey = process.env.TURNSTILE_SECRET_KEY;
+  if (!secretKey) {
+    console.warn("No TURNSTILE_SECRET_KEY set, skipping verification");
+    return true;
+  }
+
+  const formData = new FormData();
+  formData.append("secret", secretKey);
+  formData.append("response", token);
+
+  const res = await fetch(
+    "https://challenges.cloudflare.com/turnstile/v0/siteverify",
+    { method: "POST", body: formData }
+  );
+
+  const data = await res.json();
+  return data.success;
+}