Add clarifying comments for DateTimeOffset usage in date range queries

Co-authored-by: LazuliKao <46601807+LazuliKao@users.noreply.github.com>

Author: Copilot

src/HuaJiBot.NET.Plugin.Calendar/ClubAffairsReminder.cs

@@ -135,6 +135,7 @@ private void SendDailyReminder(DateTimeOffset now)
             return;
         }
 
+        // 创建明天和后天的DateTimeOffset，时间设置为00:00:00以获取整天的事务
         var tomorrow = new DateTimeOffset(now.Date.AddDays(1), now.Offset);
         var dayAfterTomorrow = new DateTimeOffset(now.Date.AddDays(2), now.Offset);
 

src/HuaJiBot.NET.UnitTest/ClubAffairsReminderTest.cs

@@ -51,6 +51,7 @@ public void TestWeekRange()
     public void TestDayRange()
     {
         // Test that tomorrow calculation is correct
+        // 创建午夜时间的DateTimeOffset以匹配生产代码中用于日期范围查询的行为
         var today = new DateTimeOffset(2024, 10, 21, 9, 0, 0, TimeSpan.FromHours(8));
         var tomorrow = new DateTimeOffset(today.Date.AddDays(1), today.Offset);
         var dayAfterTomorrow = new DateTimeOffset(today.Date.AddDays(2), today.Offset);