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.

tests/HSchool.Schedule.Tests/HSchool.Schedule.Tests.csproj

@@ -0,0 +1,31 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <RootNamespace>HSchool.Schedule.Tests</RootNamespace>
+    <IsTestProject>true</IsTestProject>
+    <OutputType>Exe</OutputType>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="xunit.v3" />
+    <PackageReference Include="xunit.runner.visualstudio" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\HSchool.Schedule\HSchool.Schedule.csproj" />
+    <ProjectReference Include="..\..\src\HSchool.Content\HSchool.Content.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Content Include="..\..\src\HSchool.Server\mods\core\**\*">
+      <Link>vanilla\%(RecursiveDir)%(Filename)%(Extension)</Link>
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
+</Project>