feat(fireworks): burst radial blanc al explotar enemic + tuning

source/game/effects/firework_manager.hpp

@@ -27,7 +27,7 @@ namespace Effects {
         //   n_points: nombre de línies. Default Defaults::FX::Firework::N_POINTS.
         //   initial_brightness: 0..1.
         void spawn(const Vec2& origen,
-            SDL_Color color,
+            SDL_Color color = Defaults::FX::Firework::DEFAULT_COLOR,
             float initial_speed = Defaults::FX::Firework::SPEED,
             int n_points = Defaults::FX::Firework::N_POINTS,
             float initial_brightness = Defaults::FX::Firework::INITIAL_BRIGHTNESS);