Add option to make off-map artillery markers optional

[scarf005]

Additions

• Adds an opt-out option Require marker for off-map artillery
  • when ON (default ON): same as before
  • when OFF: you'll be able to use off-map artillery without markers with accuracy penalty, just like in-map artillery

Reasoning

Felt weird that you can bombard other base with artillery, but cannot when your pawns are raiding said base. I think player should be able to bomb the enemy base even if there's friendlies in it (if you're willing to risk friendly fire) totally not because i got annoyed forgetting to bring radio pack binoculars for Nth time

Alternatives

add optional slider for inaccuracy modifier? but it works in this form and it's as simple as it can get

Testing

Check tests you have performed:

• Compiles without warnings
• Game runs without errors
• Playtested a quick dev playthrough, and confirmed both with-binoculars and without-binoculars work normally.

used for testing: 9 105mm howitzers targetting works without binoculars and radio pack notice the inaccuracy (targetted: base structure) binoculars work normally

Extra

AI usage disclosure: I used assistance of AI when writing code for this PR (GPT 5.6 sol on pi), and disclosed it on 820733b (this PR). everything else, including testing and this PR body, is done by human (me)

[github-actions]

You can download the rebuilt assembly for this PR here: https://combatextended.lp-programming.com/CombatExtended-30733103830.zip