fix(store): enforce UTC holiday dates and exclude deleted stores

src/Api/TakeoutSaaS.TenantApi/Controllers/StoreApiHelpers.cs

@@ -95,7 +95,8 @@ internal static class StoreApiHelpers
             throw new BusinessException(ErrorCodes.BadRequest, $"{fieldName} 日期格式必须为 yyyy-MM-dd");
         }
 
-        return parsed.Date;
+        // PostgreSQL timestamptz 仅接受 UTC，日期输入统一落盘为 UTC 零点。
+        return DateTime.SpecifyKind(parsed.Date, DateTimeKind.Utc);
     }
 
     public static string ToDateOnly(DateTime value)