fix(HEL-485): 盘中选择当天不再整页退回昨天

交易时段缺少盘后正式数据时继续展示当天盘中行情，只有开盘前、周末和历史日期才沿用最近收盘结果。

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: multica-agent <github@multica.ai>

backend/data/providers/tushare_helpers.py

@@ -6,6 +6,17 @@ from typing import Any
 from backend.data.numbers import finite_number as _number
 
 
+def calendar_is_open(value: Any) -> bool:
+    if value in (True, 1, "1", "Y", "y"):
+        return True
+    if value in (False, 0, "0", "N", "n", None, ""):
+        return False
+    try:
+        return int(value) == 1
+    except (TypeError, ValueError):
+        return False
+
+
 def _text(value: Any) -> str:
     if isinstance(value, (list, tuple, set)):
         return "、".join(str(item).strip() for item in value if str(item).strip())