Update staffing management to enhance payroll and hiring functionalities

- Increased the `MonthlyPayrollCap` from 10,000 to 40,000, allowing for greater flexibility in hiring and subject assignments.
- Revised payroll calculation logic to ensure that staff members are compensated based on their actual weekly hours, with a minimum payment reflecting one full rate.
- Updated documentation to clarify the new payroll structure and its implications for hiring and subject assignments.
- Enhanced tests to validate the new payroll cap and ensure proper functionality in staffing scenarios, including the handling of uncovered subjects.
- Improved localization strings to reflect changes in staffing and payroll terminology.

src/HSchool.Content/PeopleDefValidator.cs

@@ -327,9 +327,11 @@ internal static class PeopleDefValidator
             throw new ContentLoadException($"StaffingDef '{staffing.DefName}' monthly hours must be positive.");
         }
 
-        if (staffing.ExtraSubjectSurcharge < 0f)
+        if (staffing.MaxWeeklyHours < staffing.BaseWeeklyHours)
         {
-            throw new ContentLoadException($"StaffingDef '{staffing.DefName}' extraSubjectSurcharge cannot be negative.");
+            throw new ContentLoadException(
+                $"StaffingDef '{staffing.DefName}' maxWeeklyHours must be at least baseWeeklyHours: "
+                + "nobody can be paid for a full rate they are not allowed to work.");
         }
     }