fix: 修复外部因素数据源 - 北向资金改为南向资金，修复P0-P7全部外部因素

- P0资金面：DB数据过期时用麦蕊API获取资金流向
- P1市场情绪：去掉turnover字段依赖（DB无此字段）
- P2南向资金：北向实时数据已停公布，改用南向资金(港股通)替代
- P3美股：用腾讯财经API替代失效的AKShare接口
- P4大宗商品：用腾讯财经API替代，修复var_name解析
- P7汇率：用新浪财经API替代失效的AKShare接口
- 修复评分详情API技术得分硬编码问题
- 前端传入tech_score参数确保明细与列表分数一致

stock-html/services/market_sentiment.py

@@ -50,8 +50,7 @@ def calc_market_sentiment():
                 COUNT(*) FILTER (WHERE change_pct < 0) AS down_count,
                 COUNT(*) FILTER (WHERE change_pct = 0) AS flat_count,
                 COUNT(*) AS total,
-                COALESCE(SUM(amount), 0) AS total_amount,
-                COALESCE(PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY turnover), 0) AS turnover_median
+                COALESCE(SUM(amount), 0) AS total_amount
             FROM stock_realtime_price
             WHERE volume > 0 AND price > 0
         """)
@@ -66,7 +65,7 @@ def calc_market_sentiment():
         flat_count = int(row[4] or 0)
         total = int(row[5] or 1)
         total_amount = float(row[6] or 0) / 1e8  # 转为亿
-        turnover_median = float(row[7] or 0)
+        turnover_median = 0  # DB无turnover字段，不再使用
 
         # 涨跌停比
         up_down_ratio = round(limit_up / limit_down, 1) if limit_down > 0 else float(limit_up)