refactor: move database-related projects to separate folder

SqlData/Domain/Schedule/LectureHall.cs

@@ -0,0 +1,14 @@
+using System.Collections.Generic;
+
+namespace Mirea.Api.DataAccess.Domain.Schedule;
+
+public class LectureHall
+{
+    public int Id { get; set; }
+    public required string Name { get; set; }
+
+    public int CampusId { get; set; }
+    public Campus? Campus { get; set; }
+
+    public List<LessonAssociation>? LessonAssociations { get; set; }
+}