feat(playfield): refactor a Playfield amb animació de creació durant l'INIT_HUD

source/game/scenes/game_scene.hpp

@@ -8,7 +8,7 @@
 #include <memory>
 #include <string>
 
-#include "core/graphics/playfield_grid.hpp"
+#include "core/graphics/playfield.hpp"
 #include "core/graphics/vector_text.hpp"
 #include "core/physics/physics_world.hpp"
 #include "core/rendering/sdl_manager.hpp"
@@ -81,8 +81,8 @@ class GameScene final : public Scene {
     // Text vectorial
     Graphics::VectorText text_;
 
-    // Grilla de fons del playfield
-    Graphics::PlayfieldGrid playfield_grid_;
+    // Fons del playfield (graella + futures capes)
+    Graphics::Playfield playfield_;
 
     // [NEW] Stage system
     std::unique_ptr<StageSystem::StageSystemConfig> stage_config_;