feat(alliances): custom alliance duration lobby control (#4522)

## Description:

Replaces the "Disable alliances" toggle in the host and single-player
lobbies with a "Custom alliances" control: a toggle plus a minutes input
(0 to 15, step 1).

- 0 minutes disables alliances, same behavior as the old toggle.
- 1 to 15 sets the alliance duration in minutes.

How it works:

- Adds one game-config field, `customAllianceDuration` (minutes).
- `Config.allianceDuration()` uses it when set (and falls back to the
existing 5 minute default), and `Config.disableAlliances()` returns true
when it is 0.
- The legacy `disableAlliances` boolean is still read, so older/archived
configs keep working.
- Validation reuses the existing `parseBoundedIntegerFromInput` and
`toggle-input-card` helpers, so it behaves like the other numeric lobby
options (spawn immunity, max timer).
- The join-lobby screen shows "Alliances: {x}m", or "Alliances:
Disabled" at 0.

<img width="279" height="145" alt="image"
src="https://github.com/user-attachments/assets/5a608e18-3811-4eef-a3a6-9344aaf667fe"
/>
<img width="270" height="152" alt="image"
src="https://github.com/user-attachments/assets/9d8a4d30-51e7-4e82-8ce0-121b12af1c61"
/>
<img width="270" height="144" alt="image"
src="https://github.com/user-attachments/assets/a65b20fb-0db5-4657-a964-880fad7c864e"
/>


## 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

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

zixer._

src/server/GameServer.ts

@@ -273,6 +273,10 @@ export class GameServer {
       this.gameConfig.disableAlliances =
         gameConfig.disableAlliances ?? undefined;
     }
+    if (gameConfig.customAllianceDuration !== undefined) {
+      this.gameConfig.customAllianceDuration =
+        gameConfig.customAllianceDuration ?? undefined;
+    }
     if (gameConfig.allowedPublicIds !== undefined) {
       this.gameConfig.allowedPublicIds = gameConfig.allowedPublicIds;
       // A join whitelist and public listing are mutually exclusive: a listed