Fix nations being blocked by PVP immunity 🛡️ (#4282)

## Description:

### Problem

PVP immunity (the extended spawn immunity setting) was incorrectly
preventing AI nations from attacking human players. The intent of PVP
immunity is to protect human-vs-human combat only, but nations were
subject to the same restriction.

### Root Cause

In `canAttackPlayer()`, only `PlayerType.Bot` was exempt from checking
target immunity. Nations fell through to the same path as humans, so
when a nation tried to attack an immune human, `player.isImmune()`
returned true and the attack was blocked.

### Fix

Changed the immunity bypass condition from `this.type() ===
PlayerType.Bot` to `this.type() !== PlayerType.Human`. Now only human
attackers check target immunity. Both bots and nations bypass it (they
only check alliance status).

This does not affect nation spawn immunity
(`nationSpawnImmunityDuration`), which is a separate mechanism that
protects newly spawned nations from all attackers and continues to work
independently.

## 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:

FloPinguin

tests/Attack.test.ts

@@ -542,4 +542,82 @@ describe("Attack immunity", () => {
     expect(exec.isActive()).toBe(false);
     expect(playerA.units(UnitType.TransportShip)).toHaveLength(0);
   });
+
+  test("Nation can attack human during PVP immunity", async () => {
+    const nationInfo = new PlayerInfo(
+      "nation",
+      PlayerType.Nation,
+      null,
+      "nation_id",
+    );
+    const nation = addPlayerToGame(nationInfo, game, game.ref(15, 0));
+    game.executeNextTick();
+    game.executeNextTick();
+
+    // Nation attacks playerA during PVP immunity - should succeed
+    game.addExecution(new AttackExecution(null, nation, "playerA_id", null));
+    game.executeNextTick();
+    expect(nation.outgoingAttacks()).toHaveLength(1);
+  });
+
+  test("Bot can attack human during PVP immunity", async () => {
+    const botInfo = new PlayerInfo("bot", PlayerType.Bot, null, "bot_id");
+    const bot = addPlayerToGame(botInfo, game, game.ref(15, 0));
+    game.executeNextTick();
+    game.executeNextTick();
+
+    // Bot attacks playerA during PVP immunity - should succeed
+    game.addExecution(new AttackExecution(null, bot, "playerA_id", null));
+    game.executeNextTick();
+    expect(bot.outgoingAttacks()).toHaveLength(1);
+  });
+
+  test("Nation can attack nation during PVP immunity", async () => {
+    const nationAInfo = new PlayerInfo(
+      "nationA",
+      PlayerType.Nation,
+      null,
+      "nationA_id",
+    );
+    const nationA = addPlayerToGame(nationAInfo, game, game.ref(15, 0));
+
+    const nationBInfo = new PlayerInfo(
+      "nationB",
+      PlayerType.Nation,
+      null,
+      "nationB_id",
+    );
+    addPlayerToGame(nationBInfo, game, game.ref(15, 15));
+    game.executeNextTick();
+    game.executeNextTick();
+
+    // Nation A attacks Nation B during PVP immunity - should succeed
+    game.addExecution(new AttackExecution(null, nationA, "nationB_id", null));
+    game.executeNextTick();
+    expect(nationA.outgoingAttacks()).toHaveLength(1);
+  });
+
+  test("Nation cannot attack allied human during PVP immunity", async () => {
+    const nationInfo = new PlayerInfo(
+      "nation",
+      PlayerType.Nation,
+      null,
+      "nation_id",
+    );
+    const nation = addPlayerToGame(nationInfo, game, game.ref(15, 0));
+    game.executeNextTick();
+    game.executeNextTick();
+
+    // Create alliance between nation and playerA
+    const allianceRequest = nation.createAllianceRequest(playerA);
+    if (allianceRequest) {
+      allianceRequest.accept();
+    }
+    expect(nation.isAlliedWith(playerA)).toBe(true);
+
+    // Nation tries to attack allied playerA during immunity - should be blocked by friendliness
+    game.addExecution(new AttackExecution(null, nation, "playerA_id", null));
+    game.executeNextTick();
+    expect(nation.outgoingAttacks()).toHaveLength(0);
+  });
 });