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.

tests/HSchool.Protocol.Tests/ProtocolCodecTests.cs

@@ -164,6 +164,34 @@ public class ProtocolCodecTests
         Assert.Equal(0, read.Nodes[0].PupilSlots);
         Assert.Equal([new MapSnapshotItem("Стул", 2)], read.Nodes[1].Items);
         Assert.Equal(["Директор"], read.Nodes[1].Positions);
+        Assert.Equal("", read.Nodes[0].ActivitySubject);
+        Assert.Empty(read.Nodes[0].Present);
+    }
+
+    [Fact]
+    public void MapSnapshot_RoundTripsOccupancyAfterPositions()
+    {
+        var message = new ServerMapSnapshotMessage(3, [
+            new MapSnapshotNode(
+                3,
+                "classroom-101",
+                "floor-1",
+                "Класс 101",
+                16,
+                [new MapSnapshotItem("Парта", 16)],
+                [],
+                "Математика",
+                "5А",
+                ["Иванова Ольга Михайловна", "Соколов Иван Петрович"]),
+        ]);
+        var buffer = new byte[ProtocolCodec.MapSnapshotSize(message)];
+
+        var length = ProtocolCodec.WriteMapSnapshot(buffer, message);
+        var read = ProtocolCodec.ReadMapSnapshot(buffer.AsSpan(0, length));
+
+        Assert.Equal("Математика", read.Nodes[0].ActivitySubject);
+        Assert.Equal("5А", read.Nodes[0].ActivityClass);
+        Assert.Equal(["Иванова Ольга Михайловна", "Соколов Иван Петрович"], read.Nodes[0].Present);
     }
 
     [Fact]