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/Program.cs

@@ -51,6 +51,7 @@ app.UseWebSockets(new WebSocketOptions
 });
 
 app.MapSchoolEndpoints();
+app.MapTimetableEndpoints();
 app.MapModEndpoints();
 
 app.MapGet("/api/status", (GameLoopService loop, ClientRegistry clients) =>