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/client/graphics/layers/HeadsUpMessage.ts

@@ -16,6 +16,9 @@ export class HeadsUpMessage extends LitElement implements Layer {
   @state()
   private isPaused = false;
 
+  @state()
+  private isImmunityActive = false;
+
   @state()
   private toastMessage: string | import("lit").TemplateResult | null = null;
   @state()
@@ -79,7 +82,18 @@ export class HeadsUpMessage extends LitElement implements Layer {
       this.isPaused = pauseUpdate.paused;
     }
 
-    this.isVisible = this.game.inSpawnPhase() || this.isPaused;
+    const showImmunityHudDuration = 10 * 10;
+    const spawnEnd = this.game.config().numSpawnPhaseTurns();
+    const ticksSinceSpawnEnd = this.game.ticks() - spawnEnd;
+
+    this.isImmunityActive =
+      this.game.config().hasExtendedSpawnImmunity() &&
+      !this.game.inSpawnPhase() &&
+      this.game.isSpawnImmunityActive() &&
+      ticksSinceSpawnEnd < showImmunityHudDuration;
+
+    this.isVisible =
+      this.game.inSpawnPhase() || this.isPaused || this.isImmunityActive;
     this.requestUpdate();
   }
 
@@ -91,6 +105,11 @@ export class HeadsUpMessage extends LitElement implements Layer {
         return translateText("heads_up_message.multiplayer_game_paused");
       }
     }
+    if (this.isImmunityActive) {
+      return translateText("heads_up_message.pvp_immunity_active", {
+        seconds: Math.round(this.game.config().spawnImmunityDuration() / 10),
+      });
+    }
     return this.game.config().isRandomSpawn()
       ? translateText("heads_up_message.random_spawn")
       : translateText("heads_up_message.choose_spawn");

src/client/graphics/layers/ImmunityTimer.ts

@@ -41,7 +41,10 @@ export class ImmunityTimer extends LitElement implements Layer {
     const immunityDuration = this.game.config().spawnImmunityDuration();
     const spawnPhaseTurns = this.game.config().numSpawnPhaseTurns();
 
-    if (immunityDuration <= 5 * 10 || this.game.inSpawnPhase()) {
+    if (
+      !this.game.config().hasExtendedSpawnImmunity() ||
+      this.game.inSpawnPhase()
+    ) {
       this.setInactive();
       return;
     }