feat: Prevent GameServer from restarting after ending by introducin… (#2923)

If this PR fixes an issue, link it below. If not, delete these two
lines.
Resolves #(issue number)
#2919 


In GameManager.tick(), when a game becomes active but hasn't started, a
setTimeout for game.start() is scheduled with a 2-second delay. If the
game finishes or is cancelled within those 2 seconds, game.end() is
called, which clears the existing interval. However:

1.The 2-second timeout still fires. game.start() executes.
2. A NEW setInterval is created for turn execution.
3.Since the game is already ending/finished, it's removed from
GameManager.games, but the interval continues to run forever in the
background


## 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:

codimo

src/server/GameServer.ts

@@ -71,6 +71,8 @@ export class GameServer {
     { winner: ClientSendWinnerMessage; ips: Set<string> }
   > = new Map();
 
+  private _hasEnded = false;
+
   public desyncCount = 0;
 
   constructor(
@@ -536,7 +538,7 @@ export class GameServer {
   }
 
   public start() {
-    if (this._hasStarted) {
+    if (this._hasStarted || this._hasEnded) {
       return;
     }
     this._hasStarted = true;
@@ -639,9 +641,11 @@ export class GameServer {
   }
 
   async end() {
+    this._hasEnded = true;
     // Close all WebSocket connections
     if (this.endTurnIntervalID) {
       clearInterval(this.endTurnIntervalID);
+      this.endTurnIntervalID = undefined;
     }
     this.websockets.forEach((ws) => {
       if (ws.readyState === WebSocket.OPEN) {