feat: initial commit — GramJS Telegram relay for OpenClaw inject

Telegram userbot relay that monitors specified group chats and forwards
bot messages to OpenClaw's inject-http endpoint via webhook.

Features:
- GramJS (MTProto) for reading bot messages (invisible to Bot API)
- Media download + multipart form upload
- BOT_EXCLUDE filter (by user ID or @username)
- HTML entity formatting (bold, italic, code, pre, links, etc.)
- Graceful shutdown on SIGINT/SIGTERM
- .env configuration with validation

CLAUDE.md

@@ -0,0 +1,27 @@
+# Intergram-JS - GramJS Telegram Relay
+
+Telegram userbot，監聽指定群組訊息並轉發到 Webhook endpoint。
+GramJS (Node.js) 版本，對標 Python Telethon 版 intergram。
+
+## 技術棧
+
+- Node.js >= 22 (ESM)
+- telegram (GramJS) - Telegram userbot client
+- 原生 fetch + FormData (Node 22+ 內建)
+
+## 常用指令
+
+```bash
+# 安裝依賴
+npm install
+
+# 啟動
+node main.js
+```
+
+## 架構
+
+- `main.js` - 入口點
+- `src/config.js` - 環境變數載入與驗證
+- `src/formatter.js` - Telegram Message → Webhook JSON 轉換
+- `src/relay.js` - GramJS 事件監聽 + fetch 轉發