perf: Skip out-of-bounds entities during Grid rendering closes #52

- Add visibility bounds check in entity render loop
- Skip entities outside view with 1 cell margin
- Improves performance for large grids with many entities
- Bounds check considers zoom and pan settings

src/UIGrid.cpp

@@ -138,7 +138,13 @@ void UIGrid::render(sf::Vector2f offset, sf::RenderTarget& target)
     // middle layer - entities
     // disabling entity rendering until I can render their UISprite inside the rendertexture (not directly to window)
     for (auto e : *entities) {
-        // TODO skip out-of-bounds entities (grid square not visible at all, check for partially on visible grid squares / floating point grid position)
+        // Skip out-of-bounds entities for performance
+        // Check if entity is within visible bounds (with 1 cell margin for partially visible entities)
+        if (e->position.x < left_edge - 1 || e->position.x >= left_edge + width_sq + 1 ||
+            e->position.y < top_edge - 1 || e->position.y >= top_edge + height_sq + 1) {
+            continue; // Skip this entity as it's not visible
+        }
+        
         //auto drawent = e->cGrid->indexsprite.drawable();
         auto& drawent = e->sprite;
         //drawent.setScale(zoom, zoom);