Use WebSocket intent for lobby game configuration updates (#2761)

Fixes #2758

## Description:
This PR migrates lobby configuration updates from the HTTP PUT
`/game/:id` endpoint to a WebSocket-based intent flow.

The lobby creator is already authenticated via the game WebSocket, so
updating configuration through intents removes redundant authentication
and aligns with existing real-time lobby actions such as `kick_player`
and `toggle_pause`.

## Changes Made
- Added `update_game_config` WebSocket intent schema
- Wired client → transport → server intent handling
- Refactored `putGameConfig()` to emit WebSocket intent instead of HTTP
fetch
- Preserved all existing validation, partial-update semantics, and
client-side debouncing
- Left the REST endpoint untouched for backward compatibility

## Testing
- All existing automated tests pass
- Manual verification completed:
  - Lobby creator can update all lobby settings
  - Non-creators are rejected
  - Updates are rejected after game start
  - Bots slider debounce (300ms) remains intact
  - No `PUT /api/game/:id` requests are made from the lobby UI

## Checklist:
- [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

src/server/GameServer.ts

@@ -350,6 +350,55 @@ export class GameServer {
                 this.kickClient(clientMsg.intent.target);
                 return;
               }
+              case "update_game_config": {
+                // Only lobby creator can update config
+                if (client.clientID !== this.lobbyCreatorID) {
+                  this.log.warn(`Only lobby creator can update game config`, {
+                    clientID: client.clientID,
+                    creatorID: this.lobbyCreatorID,
+                    gameID: this.id,
+                  });
+                  return;
+                }
+
+                if (this.isPublic()) {
+                  this.log.warn(`Cannot update public game via WebSocket`, {
+                    gameID: this.id,
+                    clientID: client.clientID,
+                  });
+                  return;
+                }
+
+                if (this.hasStarted()) {
+                  this.log.warn(
+                    `Cannot update game config after it has started`,
+                    {
+                      gameID: this.id,
+                      clientID: client.clientID,
+                    },
+                  );
+                  return;
+                }
+
+                if (clientMsg.intent.config.gameType === GameType.Public) {
+                  this.log.warn(`Cannot update game to public via WebSocket`, {
+                    gameID: this.id,
+                    clientID: client.clientID,
+                  });
+                  return;
+                }
+
+                this.log.info(
+                  `Lobby creator updated game config via WebSocket`,
+                  {
+                    creatorID: client.clientID,
+                    gameID: this.id,
+                  },
+                );
+
+                this.updateGameConfig(clientMsg.intent.config);
+                return;
+              }
               case "toggle_pause": {
                 // Only lobby creator can pause/resume
                 if (client.clientID !== this.lobbyCreatorID) {