feat: add QQ channel integration with botpy SDK

Add official QQ platform support using botpy SDK with WebSocket connection.

Features:
- C2C (private message) support via QQ Open Platform
- WebSocket-based bot connection (no public IP required)
- Message deduplication with efficient deque-based LRU cache
- User whitelist support via allow_from configuration
- Clean async architecture using single event loop

Changes:
- Add QQChannel implementation in nanobot/channels/qq.py
- Add QQConfig schema with appId and secret fields
- Register QQ channel in ChannelManager
- Update README with QQ setup instructions
- Add qq-botpy dependency to pyproject.toml
- Add botpy.log to .gitignore

Setup:
1. Get AppID and Secret from q.qq.com
2. Configure in ~/.nanobot/config.json:
   {
     "channels": {
       "qq": {
         "enabled": true,
         "appId": "YOUR_APP_ID",
         "secret": "YOUR_APP_SECRET",
         "allowFrom": []
       }
     }
   }
3. Run: nanobot gateway

Note: Group chat support will be added in future updates.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

README.md

@@ -166,7 +166,7 @@ nanobot agent -m "Hello from my local LLM!"
 
 ## 💬 Chat Apps
 
-Talk to your nanobot through Telegram, Discord, WhatsApp, Feishu, DingTalk, or Email — anytime, anywhere.
+Talk to your nanobot through Telegram, Discord, WhatsApp, Feishu, DingTalk, Email, or QQ — anytime, anywhere.
 
 | Channel | Setup |
 |---------|-------|
@@ -176,6 +176,7 @@ Talk to your nanobot through Telegram, Discord, WhatsApp, Feishu, DingTalk, or E
 | **Feishu** | Medium (app credentials) |
 | **DingTalk** | Medium (app credentials) |
 | **Email** | Medium (IMAP/SMTP credentials) |
+| **QQ** | Easy (app credentials) |
 
 <details>
 <summary><b>Telegram</b> (Recommended)</summary>
@@ -335,6 +336,45 @@ nanobot gateway
 
 </details>
 
+<details>
+<summary><b>QQ (QQ私聊)</b></summary>
+
+Uses **botpy SDK** with WebSocket — no public IP required.
+
+**1. Create a QQ bot**
+- Visit [QQ Open Platform](https://q.qq.com)
+- Create a new bot application
+- Get **AppID** and **Secret** from "Developer Settings"
+
+**2. Configure**
+
+```json
+{
+  "channels": {
+    "qq": {
+      "enabled": true,
+      "appId": "YOUR_APP_ID",
+      "secret": "YOUR_APP_SECRET",
+      "allowFrom": []
+    }
+  }
+}
+```
+
+> `allowFrom`: Leave empty for public access, or add user openids to restrict access.
+> Example: `"allowFrom": ["user_openid_1", "user_openid_2"]`
+
+**3. Run**
+
+```bash
+nanobot gateway
+```
+
+> [!TIP]
+> QQ bot currently supports **private messages only**. Group chat support coming soon!
+
+</details>
+
 <details>
 <summary><b>DingTalk (钉钉)</b></summary>