Add timetable planning and related tests to school simulation

- Introduced a new project for timetable planning, dependent on HSchool.Content.
- Updated documentation to reflect the addition of timetable planning and its dependencies.
- Added tests for timetable planning to ensure deterministic behavior with the same staff and map.
- Revised architecture documentation to include the new HSchool.Schedule component and its interactions.

src/HSchool.Schedule/HSchool.Schedule.csproj

@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <RootNamespace>HSchool.Schedule</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\HSchool.Content\HSchool.Content.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <InternalsVisibleTo Include="HSchool.Schedule.Tests" />
+  </ItemGroup>
+
+</Project>