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/config/schema.py

@@ -77,6 +77,14 @@ class EmailConfig(BaseModel):
     allow_from: list[str] = Field(default_factory=list)  # Allowed sender email addresses
 
 
+class QQConfig(BaseModel):
+    """QQ channel configuration using botpy SDK."""
+    enabled: bool = False
+    app_id: str = ""  # 机器人 ID (AppID) from q.qq.com
+    secret: str = ""  # 机器人密钥 (AppSecret) from q.qq.com
+    allow_from: list[str] = Field(default_factory=list)  # Allowed user openids (empty = public access)
+
+
 class ChannelsConfig(BaseModel):
     """Configuration for chat channels."""
     whatsapp: WhatsAppConfig = Field(default_factory=WhatsAppConfig)
@@ -85,6 +93,7 @@ class ChannelsConfig(BaseModel):
     feishu: FeishuConfig = Field(default_factory=FeishuConfig)
     dingtalk: DingTalkConfig = Field(default_factory=DingTalkConfig)
     email: EmailConfig = Field(default_factory=EmailConfig)
+    qq: QQConfig = Field(default_factory=QQConfig)
 
 
 class AgentDefaults(BaseModel):