Update wire protocol to version 6 and enhance timetable functionality

- Bumped the wire protocol version to 6, reflecting changes in the communication structure.
- Expanded the timetable API with new endpoints for fetching and managing lesson schedules, including `GET /api/schools/{id}/timetable` and `POST /api/schools/{id}/timetable/pin`.
- Updated the protocol documentation to include detailed descriptions of the new timetable features and message structures.
- Enhanced the client-side implementation to support the new timetable functionalities, including lesson pinning and unpinning.
- Revised server-side logic to handle timetable operations and ensure proper integration with existing school management features.
- Added tests to validate the new timetable functionalities and ensure robustness in handling lesson data.

src/HSchool.Simulation/SchoolTimetables.cs

@@ -0,0 +1,31 @@
+using HSchool.Content;
+using HSchool.People;
+using HSchool.Schedule;
+
+namespace HSchool.Simulation;
+
+/// <summary>Turns a school's roster into planner input and back. The worker calls this, not the tick.</summary>
+public static class SchoolTimetables
+{
+    public static Timetable Build(
+        DefCatalog catalog,
+        MapLayout map,
+        Roster roster,
+        IReadOnlyList<LessonPlacement>? locked,
+        int weekDays)
+    {
+        ArgumentNullException.ThrowIfNull(catalog);
+        ArgumentNullException.ThrowIfNull(map);
+        ArgumentNullException.ThrowIfNull(roster);
+
+        var classes = roster.Classes
+            .Select(item => new PlannerClass(item.Id, item.Year, item.Letter, item.RoomId, item.PupilIds.Count))
+            .ToArray();
+        var teachers = roster.People
+            .Where(person => person.IsStaff && person.Subjects.Count > 0)
+            .Select(person => new PlannerTeacher(person.Id, person.Subjects))
+            .ToArray();
+
+        return TimetablePlanner.Build(catalog, map, classes, teachers, locked, weekDays);
+    }
+}