feat: Twilio voice webhook to reject calls on WhatsApp number

POST /webhook/twilio/voice returns TwiML that says the number doesn't
accept voice calls and hangs up — needed for Twilio number config.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/index.ts

@@ -1253,6 +1253,14 @@ app.post('/webhook/whatsapp', express.raw({ type: '*/*' }), async (req, res) =>
   }
 });
 
+// ── Twilio voice webhook — reject calls on the WhatsApp number ──
+app.post('/webhook/twilio/voice', (_req, res) => {
+  res.type('text/xml').send(
+    '<?xml version="1.0" encoding="UTF-8"?>' +
+    '<Response><Say>This number does not accept voice calls. Please visit squaremcp.com for support.</Say><Hangup/></Response>'
+  );
+});
+
 // ── Auth endpoints ──────────────────────────────────────────────
 
 app.post('/api/auth/signup', express.json(), async (req, res) => {