fix：修复禁言插件和豆包画图插件

src/plugin_system/base/base_plugin.py

@@ -167,16 +167,26 @@ class BasePlugin(ABC):
         return True
 
     def get_config(self, key: str, default: Any = None) -> Any:
-        """获取插件配置值
+        """获取插件配置值，支持嵌套键访问
 
         Args:
-            key: 配置键名
+            key: 配置键名，支持嵌套访问如 "section.subsection.key"
             default: 默认值
 
         Returns:
             Any: 配置值或默认值
         """
-        return self.config.get(key, default)
+        # 支持嵌套键访问
+        keys = key.split('.')
+        current = self.config
+        
+        for k in keys:
+            if isinstance(current, dict) and k in current:
+                current = current[k]
+            else:
+                return default
+                
+        return current
 
 
 def register_plugin(cls):