refactor: position ball internally

lib/game/components/ball.dart

@@ -7,7 +7,7 @@ class Ball extends PositionBodyComponent<PinballGame, SpriteComponent>
     with BlocComponent<GameBloc, GameState> {
   Ball({
     required Vector2 position,
-  })  : _position = position,
+  })  : _position = Vector2(position.x, position.y + ballSize.y),
         super(size: ballSize);
 
   static final ballSize = Vector2.all(2);

lib/game/pinball_game.dart

@@ -44,14 +44,7 @@ class PinballGame extends Forge2DGame
   }
 
   void spawnBall() {
-    add(
-      Ball(
-        position: Vector2(
-          plunger.body.position.x,
-          plunger.body.position.y + Ball.ballSize.y,
-        ),
-      ),
-    );
+    add(Ball(position: plunger.body.position));
   }
 
   void _addContactCallbacks() {
@@ -138,7 +131,7 @@ class PinballGame extends Forge2DGame
         position: screenToWorld(
           Vector2(
             camera.viewport.effectiveSize.x - 30,
-            camera.viewport.effectiveSize.y - Plunger.compressionDistance,
+            camera.viewport.effectiveSize.y,
           ),
         ),
       ),