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/PeopleDefs.cs

@@ -181,16 +181,19 @@ public sealed class StaffingDef : Def
 
     public float HourlyWagePerSkill { get; init; }
 
-    /// <summary>Hours assumed in the monthly base rate. Extra subjects add a surcharge on top.</summary>
+    /// <summary>
+    /// One full rate. A hired person is paid for at least this many hours even with nothing
+    /// assigned; hours beyond it are paid on top.
+    /// </summary>
     public float BaseWeeklyHours { get; init; }
 
-    public float WeeksPerMonth { get; init; }
-
     /// <summary>
-    /// Added to the monthly base for each subject after the first. <c>0.25</c> means a second
-    /// subject costs 25% of the base rate.
+    /// Most hours one person can carry. A subject whose curriculum needs more than this needs a
+    /// second teacher — the hours are then shared between them.
     /// </summary>
-    public float ExtraSubjectSurcharge { get; init; }
+    public float MaxWeeklyHours { get; init; }
+
+    public float WeeksPerMonth { get; init; }
 }
 
 public enum BodyAttributeKind