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.Server/Game/WorkerCommand.cs

@@ -37,4 +37,19 @@ internal abstract record WorkerCommand
         string PersonId,
         string Subject,
         TaskCompletionSource<StaffingOutcome> Result) : WorkerCommand;
+
+    internal sealed record PinLesson(
+        string ClassId,
+        string Subject,
+        string RoomId,
+        int Day,
+        int Period,
+        TaskCompletionSource<TimetableOutcome> Result) : WorkerCommand;
+
+    internal sealed record UnpinLesson(
+        string ClassId,
+        string Subject,
+        int Day,
+        int Period,
+        TaskCompletionSource<TimetableOutcome> Result) : WorkerCommand;
 }