change to physics based ship movement

src/ui/GameWorldView.cpp

@@ -810,10 +810,7 @@ void GameWorldView::drawShips(QPainter& painter)
         if (it == m_visuals->ships.end()) { continue; }
 
         const QPointF center = worldToWidget(ship.position);
-        const QVector2D vel  = ship.velocity;
-        const QVector2D dir  = (vel.length() > 0.0001f)
-            ? vel.normalized()
-            : QVector2D(1.0f, 0.0f);
+        const QVector2D dir(std::cos(ship.facing), std::sin(ship.facing));
         const QVector2D perp(-dir.y(), dir.x());
 
         const float fwd  = tilePx() * 0.45f;