Enhance school creation and staffing management with native language support

- Updated protocol documentation to include `nativeLanguages` in `nameSets` and added `nativeLanguage` to school creation options.
- Enhanced the UI for school creation to allow selection of native languages, improving user experience.
- Revised API interfaces to accommodate new native language features, ensuring proper data handling.
- Improved localization strings to support new native language functionalities in both English and Russian.
- Updated tests to validate the new native language features and ensure robust functionality in staffing scenarios.

src/HSchool.People/NativeLanguages.cs

@@ -0,0 +1,38 @@
+namespace HSchool.People;
+
+/// <summary>
+/// A name set can speak several native languages; the school picks one. Empty request rolls from
+/// the school seed so the same create always lands on the same tongue.
+/// </summary>
+public static class NativeLanguages
+{
+    public static bool Allows(NameSetDef names, string skill) =>
+        names.Spoken.Contains(skill, StringComparer.Ordinal);
+
+    /// <summary>
+    /// <paramref name="requested"/> must already be in the set, or empty. Invalid ids return
+    /// null so the create path can 400. When omitted, a new school rolls; a reload without a
+    /// saved pick takes the first listed language so old saves do not reshuffle intake.
+    /// </summary>
+    public static string? Pick(NameSetDef names, int schoolSeed, string? requested, bool rollIfOmitted)
+    {
+        var spoken = names.Spoken;
+        if (spoken.Count == 0)
+        {
+            return null;
+        }
+
+        if (!string.IsNullOrWhiteSpace(requested))
+        {
+            return Allows(names, requested) ? requested : null;
+        }
+
+        if (!rollIfOmitted || spoken.Count == 1)
+        {
+            return spoken[0];
+        }
+
+        var rng = new Random(Seed.ForSchool(schoolSeed, Seed.NativeLanguageSalt));
+        return spoken[rng.Next(spoken.Count)];
+    }
+}