Enhance staffing management in school simulation by introducing API endpoints for hiring staff and assigning subjects. Implement payroll cap validation to ensure hiring and subject assignments do not exceed the allocated budget. Update the simulation options to include a monthly payroll cap and revise related classes to support new staffing functionalities. Enhance documentation to reflect these changes and update tests to validate the new features.

src/HSchool.Server/Program.cs

@@ -21,6 +21,7 @@ builder.Services
     .Validate(options => !string.IsNullOrWhiteSpace(options.SavesDirectory), "Simulation:SavesDirectory must be set.")
     .Validate(options => !string.IsNullOrWhiteSpace(options.ModsDirectory), "Simulation:ModsDirectory must be set.")
     .Validate(options => options.SaveIntervalSeconds is > 0 and <= 3600, "Simulation:SaveIntervalSeconds must be between 1 and 3600.")
+    .Validate(options => options.MonthlyPayrollCap > 0, "Simulation:MonthlyPayrollCap must be positive.")
     .ValidateOnStart();
 
 builder.Services.AddSingleton<GameCommandQueue>();