Add PVP immunity to 5M starting gold modifier games 🔧 (#3180)

## Description:

Adds 30 seconds of PVP immunity to 5M starting gold modifier games.
So you cannot insta-nuke other players.

Because I'm sure people would be confused "I cannot attack!!!!" I added
a HeadsUpMessage which informs about the PVP immunity.
We already have a ImmunityTimer progress bar but I don't think its
enough.

<img width="1270" height="745" alt="image"
src="https://github.com/user-attachments/assets/0ee23dc4-1c7b-4d62-8b3d-8de214f03c2b"
/>

I had a second count in the HeadsUpMessage (seconds until PVP immunity
is over) but it felt too busy. So I removed it. You can tell when PVP
immunity is over by looking at the progress bar.

## 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:

FloPinguin

---------

Co-authored-by: Evan <evanpelle@gmail.com>

src/server/MapPlaylist.ts

@@ -160,7 +160,7 @@ export class MapPlaylist {
       gameMode: mode,
       playerTeams,
       bots: isCompact ? 100 : 400,
-      spawnImmunityDuration: 5 * 10,
+      spawnImmunityDuration: startingGold ? 30 * 10 : 5 * 10,
       disabledUnits: [],
     } satisfies GameConfig;
   }