fix(zalo): fix pairing channel detection and webhook payload format

Amp-Thread-ID: https://ampcode.com/threads/T-019bc4e0-fcb1-77be-b0b5-0d498f0c7197
Co-authored-by: Amp <amp@ampcode.com>

src/pairing/pairing-labels.ts

@@ -1,6 +1,6 @@
-import { requirePairingAdapter } from "../channels/plugins/pairing.js";
+import { getPairingAdapter } from "../channels/plugins/pairing.js";
 import type { PairingChannel } from "./pairing-store.js";
 
 export function resolvePairingIdLabel(channel: PairingChannel): string {
-  return requirePairingAdapter(channel).idLabel;
+  return getPairingAdapter(channel)?.idLabel ?? "userId";
 }