Add WeChat Channel

Adds WeChat support via iLink Bot API — the first-party Tencent API for personal WeChat bots (different from WeCom / Official Account).

Why this is different from wechaty/PadLocal:

• Official Tencent API — no ToS violation, no ban risk
• Free — no PadLocal token required
• No public webhook URL needed — uses long-poll
• Works with any personal WeChat account

Prerequisites

• A personal WeChat account with the mobile app installed
• A phone to scan the QR code for login
• Node.js >= 20 (already required by NanoClaw)

Install