adds map of the Balkans (using Additional nations feature) (#3998)

## Description:

Adds map of the Balkan Peninsula and surroundings. Heavily requested map
with multiple posts on the Discord all with over 10 or 20 upvotes.

23 NPC/Nations based on countries and relevant regions of the area. Adds
an extra 39 nations for crowded Humans vs Nations gamemode for a total
of 62 NPCs, based on regions of multiple countries. Also some flags for
some regions.

Source from NASA DEM, already credited

Photo of base map, and 62 HvN:


<img width="614" height="588" alt="Captura de pantalla 2026-05-24
030105"
src="https://github.com/user-attachments/assets/5742a4c3-1b1f-4ca7-858d-91529861dd81"
/>

<img width="548" height="547" alt="image"
src="https://github.com/user-attachments/assets/758d8ad0-1515-41b8-8d42-14e76cdd54ed"
/>

This map completes the quartet row of "polemic" maps for v32

<img width="678" height="119" alt="image"
src="https://github.com/user-attachments/assets/9e6f4ef1-f0cc-48ea-a59f-b7ff69033b73"
/>

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

tri.star1011

src/core/game/Game.ts

@@ -175,6 +175,7 @@ export enum GameMapType {
   DanishStraits = "Danish Straits",
   NorthwestPassage = "Northwest Passage",
   Venice = "Venice",
+  Balkans = "Balkans",
 }
 
 export type GameMapName = keyof typeof GameMapType;
@@ -238,6 +239,7 @@ export const mapCategories: Record<string, GameMapType[]> = {
     GameMapType.BajaCalifornia,
     GameMapType.MiddleEast,
     GameMapType.TaiwanStrait,
+    GameMapType.Balkans,
     GameMapType.IndianSubcontinent,
     GameMapType.DanishStraits,
     GameMapType.NorthwestPassage,

src/server/MapPlaylist.ts

@@ -43,6 +43,7 @@ const FREQUENCY: Partial<Record<GameMapName, number>> = {
   Australia: 4,
   Baikal: 5,
   BajaCalifornia: 4,
+  Balkans: 6,
   BeringSea: 5,
   BeringStrait: 2,
   BetweenTwoSeas: 5,