调整趋势图功能，加入了查询数据库，分析群聊聊天数量的功能

db/message_storage.py

@@ -84,4 +84,27 @@ class MessageStorageDB(BaseDBOperator):
         ON DUPLICATE KEY UPDATE count = VALUES(count)
         """
         params = (group_id, wx_id, date, count)
-        return self.execute_update(sql, params)
+        return self.execute_update(sql, params)
+    
+    
+    def get_message_trend(self, group_id: str, days: int = 7) -> List[Dict]:
+        """获取指定群组的消息趋势数据
+        
+        Args:
+            group_id: 群组ID
+            days: 获取最近几天的数据，默认7天
+            
+        Returns:
+            包含日期和消息数量的列表
+        """
+        sql = """
+        SELECT 
+            DATE(timestamp) as date,
+            COUNT(*) as message_count
+        FROM messages
+        WHERE group_id = %s
+        AND timestamp >= DATE_SUB(CURDATE(), INTERVAL %s DAY)
+        GROUP BY DATE(timestamp)
+        ORDER BY date
+        """
+        return self.execute_query(sql, (group_id, days)) or []