feat: implement verification page

apps/landing/src/app/(auth)/verification/_http/fetch-post-verify-turnstile.ts

@@ -0,0 +1,41 @@
+export async function fetchPostverifyTurnstile(
+  token: string,
+  remoteIp?: string
+): Promise<boolean> {
+  const url = 'https://challenges.cloudflare.com/turnstile/v0/siteverify';
+  const params = new URLSearchParams({
+    secret: String(process.env.TURNSTILE_SECRET_KEY),
+    response: token,
+  });
+  if (remoteIp) {
+    params.append('remoteip', remoteIp);
+  }
+
+  const res = await fetch(url, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/x-www-form-urlencoded',
+    },
+    body: params.toString(),
+  });
+
+  if (!res.ok) {
+    console.error('Turnstile verify HTTP error', res.status);
+    return false;
+  }
+
+  const data = (await res.json()) as TurnstileVerifyResponse;
+  if (!data.success) {
+    console.warn('Turnstile failure', data['error-codes']);
+    return false;
+  }
+
+  return true;
+}
+
+interface TurnstileVerifyResponse {
+  success: boolean;
+  challenge_ts: string;
+  hostname: string;
+  'error-codes'?: string[];
+}