feat(enemy): afegir behaviors WANDER/CHASE/FLEE i target multi-ship

source/game/scenes/game_scene.cpp

@@ -186,7 +186,7 @@ GameScene::GameScene(SDLManager& sdl, SceneContext& context)
     // Registramos el body al world incluso inactivo: con radius=0 no colisiona
     // ni se mueve, y al init() del stage system se activa sin re-registrar.
     for (auto& enemy : enemies_) {
-        enemy.setShipPosition(&ships_[0].getCenter());  // Set ship reference (P1 for now)
+        enemy.setShips(ships_.data(), &ships_[1]);
         physics_world_.addBody(&enemy.getBody());
         // DON'T call enemy.init() here - stage system handles spawning
     }