Configurable immunity timer (#2763)

## Description:

Resolve discussions about stalled PR
https://github.com/openfrontio/OpenFrontIO/pull/2460

<img width="724" height="348" alt="image"
src="https://github.com/user-attachments/assets/c2c9fa79-cace-431a-9ca4-b3656612fa9d"
/>

Changes:
- Added a `Player::canAttackPlayer(other)` function to determine whether
a player can be attacked.
- This function is now used in most places where a fight can occur:
    - AttackExecution (land attacks)
    - Naval invasion
    - Warship fight
- Nukes can't be thrown during the truce
- Immunity only affect human players. Nations and bot will fight as
usual, and can be fought against.
- The immunity timer uses minutes in the modal window.

UI:

- The immunity phase is displayed with a timer bar at the top. This is
from the original PR, to be discussed if it's not deemed visible enough:

<img width="632" height="215" alt="image"
src="https://github.com/user-attachments/assets/f5ab9aa0-bd4f-4503-b8d6-b40b121fba65"
/>


## 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:

IngloriousTom

---------

Co-authored-by: newyearnewphil <git@nynp.dev>

resources/lang/debug.json

@@ -145,6 +145,7 @@
     "options_title": "host_modal.options_title",
     "bots": "host_modal.bots",
     "bots_disabled": "host_modal.bots_disabled",
+    "player_immunity_duration": "host_modal.player_immunity_duration",
     "disable_nations": "host_modal.disable_nations",
     "instant_build": "host_modal.instant_build",
     "random_spawn": "host_modal.random_spawn",

resources/lang/en.json

@@ -307,6 +307,7 @@
     "options_title": "Options",
     "bots": "Bots: ",
     "bots_disabled": "Disabled",
+    "player_immunity_duration": "PVP immunity duration (minutes)",
     "nations": "Nations: ",
     "disable_nations": "Disable Nations",
     "max_timer": "Game length (minutes)",