新增每门课程的“优先上课日 / 偏好节次范围”，与硬性可排范围分离。

遗传算法在满足冲突、容量、场地等硬约束后，优先满足课程偏好；偏好无法满足时仍会安排可行课次。
管理员可通过“课程偏好权重”控制偏好的影响程度。
修复遗传适应度：教室容量冗余、同一任务分散、日负载和实验场地偏好现在都会实际参与种群评分

src/Jiaowu.Api/Domain/Academic/ScheduleEntities.cs

@@ -58,6 +58,7 @@ public sealed class ScheduleOptimizationSettings : EntityBase
     public int EarlyPeriodPenalty { get; set; } = 30;
     public int LatePeriodPenalty { get; set; } = 30;
     public int RoomCapacityWasteWeight { get; set; } = 1;
+    public int CoursePreferenceWeight { get; set; } = 180;
 
     public static ScheduleOptimizationSettings CreateDefault(Guid academicTermId) =>
         new() { AcademicTermId = academicTermId };
@@ -79,6 +80,9 @@ public sealed class TeachingTaskScheduleConstraint : EntityBase
     public string? AllowedDayOfWeeks { get; set; }
     public int? EarliestPeriod { get; set; }
     public int? LatestPeriod { get; set; }
+    public string? PreferredDayOfWeeks { get; set; }
+    public int? PreferredEarliestPeriod { get; set; }
+    public int? PreferredLatestPeriod { get; set; }
     public TeachingVenueNature AllowedExperimentVenueNatures { get; set; }
     public ICollection<TeachingTaskAllowedClassroom> AllowedClassrooms { get; set; } = [];
     public ICollection<TeachingTaskAllowedExperimentClassroom> AllowedExperimentClassrooms { get; set; } = [];