Add Japan map (#2106)

## Description:

This PR adds a new Japan map.

<img width="975" height="967" alt="スクリーンショット 2025-09-28 18 06 11"
src="https://github.com/user-attachments/assets/5ef06c1a-f020-4109-a5df-3cba7a9a074f"
/>

## 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:

aotumuri

src/client/components/Maps.ts

@@ -32,6 +32,7 @@ export const MapDescription: Record<keyof typeof GameMapType, string> = {
   Halkidiki: "Halkidiki",
   StraitOfGibraltar: "Strait of Gibraltar",
   Italia: "Italia",
+  Japan: "Japan",
   Yenisei: "Yenisei",
   Pluto: "Pluto",
   Montreal: "Montreal",

src/core/configuration/DefaultConfig.ts

@@ -63,6 +63,7 @@ const numPlayersConfig = {
   [GameMapType.Halkidiki]: [100, 50, 40],
   [GameMapType.Iceland]: [50, 40, 30],
   [GameMapType.Italia]: [50, 30, 20],
+  [GameMapType.Japan]: [20, 15, 10],
   [GameMapType.Mars]: [70, 40, 30],
   [GameMapType.Mena]: [70, 50, 40],
   [GameMapType.Montreal]: [60, 40, 30],

src/core/game/Game.ts

@@ -82,6 +82,7 @@ export enum GameMapType {
   Halkidiki = "Halkidiki",
   StraitOfGibraltar = "Strait of Gibraltar",
   Italia = "Italia",
+  Japan = "Japan",
   Yenisei = "Yenisei",
   Pluto = "Pluto",
   Montreal = "Montreal",
@@ -116,6 +117,7 @@ export const mapCategories: Record<string, GameMapType[]> = {
     GameMapType.Halkidiki,
     GameMapType.StraitOfGibraltar,
     GameMapType.Italia,
+    GameMapType.Japan,
     GameMapType.Yenisei,
     GameMapType.Montreal,
   ],

src/server/MapPlaylist.ts

@@ -38,6 +38,7 @@ const frequency: Partial<Record<GameMapName, number>> = {
   Halkidiki: 4,
   Iceland: 4,
   Italia: 6,
+  Japan: 6,
   Mars: 3,
   Mena: 6,
   Montreal: 6,