feat: add seating plans for learning groups

LehrerApp.Data.Tests/RepositoryTests.cs

@@ -189,6 +189,9 @@ public sealed class RepositoryTests
         var sectionId = Guid.NewGuid();
         db.ParticipationSections.Insert(new ParticipationSection { Id = sectionId, GroupId = groupId });
 
+        var seatingPlanId = Guid.NewGuid();
+        db.SeatingPlans.Insert(new SeatingPlan { Id = seatingPlanId, GroupId = groupId, Name = "Raumplan" });
+
         var documentationId = Guid.NewGuid();
         db.Documentation.Insert(new Documentation { Id = documentationId, GroupId = groupId, StudentId = studentId });
 
@@ -214,6 +217,7 @@ public sealed class RepositoryTests
         Assert.Null(db.ReportGrades.FindById(reportGradeId));
         Assert.Null(db.GradingSchemes.FindById(gradingSchemeId));
         Assert.Null(db.ParticipationSections.FindById(sectionId));
+        Assert.Null(db.SeatingPlans.FindById(seatingPlanId));
         Assert.Null(db.Documentation.FindById(documentationId)?.GroupId);
         Assert.Null(db.Tasks.FindById(taskId)?.GroupId);
         Assert.Null(db.TimeEntries.FindById(timeEntryId)?.GroupId);
@@ -241,6 +245,60 @@ public sealed class RepositoryTests
 
     // ── GroupMembershipRepository ────────────────────────────────────────────
 
+    [Fact]
+    public void SeatingPlanRepository_SpeichertMehrerePlaeneUndEindeutigeZuordnungen()
+    {
+        using var db = NewInMemoryContext();
+        var group = new LearningGroup { Name = "8a", SchoolYear = "2025/26" };
+        new GroupRepository(db).Save(group);
+        var anna = new Student { FirstName = "Anna", LastName = "A" };
+        var ben = new Student { FirstName = "Ben", LastName = "B" };
+        db.Students.InsertBulk([anna, ben]);
+        db.Memberships.InsertBulk([
+            new GroupMembership { GroupId = group.Id, StudentId = anna.Id },
+            new GroupMembership { GroupId = group.Id, StudentId = ben.Id },
+        ]);
+        var repo = new SeatingPlanRepository(db);
+        repo.Save(new SeatingPlan
+        {
+            GroupId = group.Id, Name = "Standard", Room = "B204", Rows = 2, Columns = 2,
+            Assignments = [new SeatAssignment { Row = 0, Column = 0, StudentId = anna.Id }],
+        });
+        repo.Save(new SeatingPlan
+        {
+            GroupId = group.Id, Name = "Standard", Room = "Physik", Rows = 2, Columns = 3,
+            Assignments = [new SeatAssignment { Row = 1, Column = 2, StudentId = ben.Id }],
+        });
+
+        var plans = repo.GetByGroup(group.Id);
+
+        Assert.Equal(2, plans.Count);
+        Assert.Contains(plans, p => p.Room == "B204" && p.Assignments.Single().StudentId == anna.Id);
+        Assert.Contains(plans, p => p.Room == "Physik" && p.Assignments.Single().StudentId == ben.Id);
+    }
+
+    [Fact]
+    public void SeatingPlanRepository_LehntDoppeltZugeordnetenSchuelerAb()
+    {
+        using var db = NewInMemoryContext();
+        var group = new LearningGroup { Name = "8a", SchoolYear = "2025/26" };
+        new GroupRepository(db).Save(group);
+        var student = new Student { FirstName = "Anna", LastName = "A" };
+        db.Students.Insert(student);
+        db.Memberships.Insert(new GroupMembership { GroupId = group.Id, StudentId = student.Id });
+        var plan = new SeatingPlan
+        {
+            GroupId = group.Id, Name = "Standard", Rows = 2, Columns = 2,
+            Assignments =
+            [
+                new SeatAssignment { Row = 0, Column = 0, StudentId = student.Id },
+                new SeatAssignment { Row = 0, Column = 1, StudentId = student.Id },
+            ],
+        };
+
+        Assert.Throws<InvalidOperationException>(() => new SeatingPlanRepository(db).Save(plan));
+    }
+
     [Fact]
     public void GroupMembershipRepository_Save_LehntZweiteZuordnungFuerGleichesPaarAb()
     {