juc - Neolithic Turrets

Adds two early-game turret options to help defend your colony before electricity:

• Stone Sling Turret – A simple, low-cost defense that hurls rocks at incoming threats.
  Research: Sling Turret (unlocked after researching Stonecutting).
• Arrow Turret – An automatic crossbow-style turret with improved range and accuracy.
  Research: Arrow Turret (requires Greatbow and Recurve Bow before unlocking).

Both turrets are buildable from primitive materials and designed to fit naturally into tribal or low-tech playthroughs without disrupting game balance.