price_monitor港股币种修复+calc_total_mv汇兑处理

问题链：
  price_monitor 从东方财富/腾讯拿HK股价(HKD) → x0.87转CNY写portfolio
  → DB存CNY→下游混读→建滔显示-24%浮亏（实为-0.6%）
修复：
  price_monitor不转CNY，港股存HKD原值
  calc_total_mv()增加币种判断：HK股用get_hk_rate()转CNY再汇总
  portfolio.json/watchlist的HK股价全部HKD原值
  DB同步修正所有HK股价格为HKD
  price_monitor DB写入加3次重试+database locked timeout
验证：
  建滔 87.7 HKD 浮亏-0.6%（不是-24%）
  现金 132,121.93 总资产 956,714.68

price_monitor.py

@@ -251,13 +251,12 @@ def refresh_data_prices():
         if s['code'] in prices:
             price, _, change_pct = prices[s['code']]
             if price > 0:
-                # 港股：API返回HKD，需转RMB
-                if is_hk_stock(s['code']):
-                    price = round(price * HK_RATE, 2)
+                # 港股API返回HKD，直接存HKD原值。calc_total_mv统一做CNY折算
                 old = s.get('price', 0)
                 if abs(old - price) > 0.001:
                     s['price'] = round(price, 2)
                     s['change_pct'] = float(change_pct) if change_pct else 0
+                    s['currency'] = 'HKD' if is_hk_stock(s['code']) else 'CNY'
                     updated += 1
                     changed = True
     if changed:
@@ -298,9 +297,6 @@ def refresh_data_prices():
         if s['code'] in prices:
             price, _, change_pct = prices[s['code']]
             if price > 0:
-                # 港股：API返回HKD，需转RMB
-                if is_hk_stock(s['code']):
-                    price = round(price * HK_RATE, 2)
                 old = s.get('price', 0)
                 if abs(old - price) > 0.001:
                     s['price'] = round(price, 2)