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>

nanobot/channels/manager.py

@@ -106,6 +106,18 @@ class ChannelManager:
                 logger.info("Email channel enabled")
             except ImportError as e:
                 logger.warning(f"Email channel not available: {e}")
+
+        # QQ channel
+        if self.config.channels.qq.enabled:
+            try:
+                from nanobot.channels.qq import QQChannel
+                self.channels["qq"] = QQChannel(
+                    self.config.channels.qq,
+                    self.bus,
+                )
+                logger.info("QQ channel enabled")
+            except ImportError as e:
+                logger.warning(f"QQ channel not available: {e}")
     
     async def _start_channel(self, name: str, channel: BaseChannel) -> None:
         """Start a channel and log any exceptions."""