feat(enemy): sistema d'HP declaratiu i nou enemic big_pentagon

source/game/entities/enemy.cpp

@@ -133,6 +133,9 @@ void Enemy::init(EnemyType type, const Vec2* ship_pos) {
     invulnerability_timer_ = cfg.spawn.invulnerability_duration;
     brightness_ = cfg.spawn.invulnerability_brightness_start;
 
+    health_ = cfg.health;
+    flash_timer_ = 0.0F;
+
     is_active_ = true;
 }
 
@@ -150,6 +153,11 @@ void Enemy::update(float delta_time) {
         }
     }
 
+    if (flash_timer_ > 0.0F) {
+        flash_timer_ -= delta_time;
+        flash_timer_ = std::max(flash_timer_, 0.0F);
+    }
+
     if (invulnerability_timer_ > 0.0F) {
         invulnerability_timer_ -= delta_time;
         invulnerability_timer_ = std::max(invulnerability_timer_, 0.0F);
@@ -192,7 +200,15 @@ void Enemy::draw() const {
         }
     }
 
-    Rendering::renderShape(renderer_, shape_, center_, rotation_, SCALE, 1.0F, brightness_, color);
+    // Flash d'impacte parcial (HP>1): força el color a blanc i el brillo a
+    // 1.0 durant la finestra de flash. Té prioritat sobre el blink wounded.
+    float effective_brightness = brightness_;
+    if (flash_timer_ > 0.0F) {
+        color = SDL_Color{.r = 255, .g = 255, .b = 255, .a = 255};
+        effective_brightness = 1.0F;
+    }
+
+    Rendering::renderShape(renderer_, shape_, center_, rotation_, SCALE, 1.0F, effective_brightness, color);
 }
 
 void Enemy::destroy() {
@@ -203,6 +219,7 @@ void Enemy::destroy() {
     wounded_timer_ = 0.0F;
     wound_expired_this_frame_ = false;
     last_hit_by_ = 0xFF;
+    flash_timer_ = 0.0F;
 }
 
 void Enemy::hurt(uint8_t shooter_id) {