已继续完成“学籍异动”后端基础闭环：

学生可申请休学、复学或退学。
自动根据当前状态推导目标学籍状态。
同一学生不能同时提交多项在审申请。
强制执行辅导员 → 学院 → 校级三级审核。
驳回不会修改学生档案。
只有校级最终批准才更新学籍状态。
数据范围分别限制到本人、所带班级、所属学院或全校。
SQLite 增量升级和 MySQL 迁移已生成。
当前 28 项测试继续全部通过。

src/Jiaowu.Api/Infrastructure/Persistence/DevelopmentSqliteMigrator.cs

@@ -14,6 +14,7 @@ public sealed class DevelopmentSqliteMigrator(
     private const string CourseSelectionMigration = "20260724_06_course_selection";
     private const string GradesMigration = "20260724_07_grades";
     private const string ExamsMigration = "20260724_08_exams";
+    private const string StudentStatusChangesMigration = "20260724_09_student_status_changes";
 
     public async Task MigrateAsync(CancellationToken cancellationToken = default)
     {
@@ -70,6 +71,10 @@ public sealed class DevelopmentSqliteMigrator(
             GradesStatements,
             cancellationToken);
         await ApplyMigrationAsync(ExamsMigration, ExamsStatements, cancellationToken);
+        await ApplyMigrationAsync(
+            StudentStatusChangesMigration,
+            StudentStatusChangesStatements,
+            cancellationToken);
     }
 
     private async Task ApplyMigrationAsync(
@@ -614,4 +619,22 @@ public sealed class DevelopmentSqliteMigrator(
         """,
         """CREATE INDEX IF NOT EXISTS "IX_ExamSessionInvigilators_TeacherId" ON "ExamSessionInvigilators" ("TeacherId");"""
     ];
+
+    private static readonly string[] StudentStatusChangesStatements =
+    [
+        """
+        CREATE TABLE IF NOT EXISTS "StudentStatusChanges" (
+            "Id" TEXT NOT NULL CONSTRAINT "PK_StudentStatusChanges" PRIMARY KEY,
+            "StudentId" TEXT NOT NULL, "Type" INTEGER NOT NULL,
+            "OriginalStatus" INTEGER NOT NULL, "TargetStatus" INTEGER NOT NULL,
+            "Reason" TEXT NOT NULL, "State" INTEGER NOT NULL,
+            "ReviewComment" TEXT NULL, "SubmittedAt" TEXT NOT NULL,
+            "ReviewedAt" TEXT NULL, "ApprovedAt" TEXT NULL,
+            "CreatedAt" TEXT NOT NULL, "UpdatedAt" TEXT NOT NULL,
+            CONSTRAINT "FK_StudentStatusChanges_Students_StudentId"
+              FOREIGN KEY ("StudentId") REFERENCES "Students" ("Id") ON DELETE RESTRICT
+        );
+        """,
+        """CREATE INDEX IF NOT EXISTS "IX_StudentStatusChanges_StudentId_State" ON "StudentStatusChanges" ("StudentId", "State");"""
+    ];
 }