feat(datasource): 股票info字段放到API响应最外层

- yfinance_source.py: stock_info 存储在 df.attrs['info'] 中
- flask_server.py: dataframe_to_json 从 df.attrs 提取 info 放到最外层
- flask_server.py: 缓存切片函数保留 info 字段
- Dockerfile: 启用 Flask 服务作为默认 CMD（端口80）

响应结构示例:
{
  "data": [{"date": "2024-01-01", "code": "AAPL", ...}],
  "info": {"sector": "Technology", "industry": "...", ...}
}

datasource/yfinance_source.py

@@ -55,6 +55,7 @@ class YFinanceSource:
         
         Returns:
             DataFrame with columns: date, open, high, low, close, volume
+            股票元信息存储在 df.attrs['info'] 中
         """
         import yfinance as yf
         
@@ -67,6 +68,13 @@ class YFinanceSource:
         try:
             ticker = yf.Ticker(yf_code)
             
+            # 获取股票信息（仅对股票/ETF有效，指数可能没有）
+            stock_info = {}
+            try:
+                stock_info = ticker.info or {}
+            except Exception:
+                pass  # 指数可能没有info
+            
             # end_date 需要加一天（yfinance的end是排他的）
             end_dt = datetime.strptime(end_date, "%Y-%m-%d") + timedelta(days=1)
             
@@ -96,6 +104,10 @@ class YFinanceSource:
             # 添加代码列
             df["code"] = code
             
+            # 将股票信息存储到 DataFrame.attrs 中（最外层结构）
+            df.attrs['info'] = stock_info
+            df.attrs['code'] = code
+            
             return df[['code', 'open', 'high', 'low', 'close', 'volume']]
             
         except Exception as e: