选课批次：时间窗口、退课截止、学分上限、开放/关闭。

教学班投放：容量、班级范围、全校开放。
学生选退课：容量、重复课程、学分上限、课表冲突校验。
教学班实时名单。
校级、学院级、学生角色分级操作。
SQLite 本地增量升级及演示数据。
MySQL 正式 EF Core 迁移。
Vue 已编译进 wwwroot，单服务运行无需 npm run dev。
学生端和管理端均完成桌面、手机响应式检查。

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

@@ -0,0 +1,54 @@
+using Jiaowu.Api.Domain.Common;
+
+namespace Jiaowu.Api.Domain.Academic;
+
+public sealed class CourseSelectionRound : EntityBase
+{
+    public Guid AcademicTermId { get; set; }
+    public AcademicTerm? AcademicTerm { get; set; }
+    public required string Name { get; set; }
+    public DateTime StartsAt { get; set; }
+    public DateTime EndsAt { get; set; }
+    public DateTime WithdrawalEndsAt { get; set; }
+    public decimal MaxCredits { get; set; } = 30;
+    public CourseSelectionRoundStatus Status { get; set; } =
+        CourseSelectionRoundStatus.Draft;
+    public string? Notes { get; set; }
+    public ICollection<CourseSelectionOffering> Offerings { get; set; } = [];
+}
+
+public sealed class CourseSelectionOffering : EntityBase
+{
+    public Guid CourseSelectionRoundId { get; set; }
+    public CourseSelectionRound? CourseSelectionRound { get; set; }
+    public Guid TeachingTaskId { get; set; }
+    public TeachingTask? TeachingTask { get; set; }
+    public int Capacity { get; set; }
+    public bool IsOpenToAll { get; set; }
+    public string? Notes { get; set; }
+    public ICollection<CourseEnrollment> Enrollments { get; set; } = [];
+}
+
+public sealed class CourseEnrollment : EntityBase
+{
+    public Guid CourseSelectionOfferingId { get; set; }
+    public CourseSelectionOffering? CourseSelectionOffering { get; set; }
+    public Guid StudentId { get; set; }
+    public Student? Student { get; set; }
+    public CourseEnrollmentStatus Status { get; set; } = CourseEnrollmentStatus.Enrolled;
+    public DateTime EnrolledAt { get; set; } = DateTime.UtcNow;
+    public DateTime? WithdrawnAt { get; set; }
+}
+
+public enum CourseSelectionRoundStatus
+{
+    Draft = 1,
+    Open = 2,
+    Closed = 3
+}
+
+public enum CourseEnrollmentStatus
+{
+    Enrolled = 1,
+    Withdrawn = 2
+}