feat(chat): add promotional external entry flow

src/lib/chat/chat_external_browser.ts

@@ -25,10 +25,10 @@ export async function openChatInExternalBrowser(): Promise<void> {
     UrlLauncherUtil.openUrlWithExternalBrowser(ROUTES.externalEntry, {
       queryParams: {
         target: "chat",
-        deviceId,
+        device_id: deviceId,
         asid,
         ...(psid ? { psid } : {}),
-        ...(avatarUrl ? { avatarUrl } : {}),
+        ...(avatarUrl ? { avatar_url: avatarUrl } : {}),
       },
     });
     return;