WIP TileView: Wheel scroll, item textures, UI left click handling
- Add mouseWheel/mouseWheelInternal to NodeUi event system
- Add mouse wheel scroll to TileView with clamped scroll range
- Fix mouseMotionInternal to keep mouseCapture across frames
- Add mouseBtnDownInternal capture forwarding
- Add left mouse button handling in gameplay UI mode
- Add mouse wheel event forwarding in gameplay
- Add Item constructor taking a Tex reference
- Wire TileViewItem::setItem to swap texture
- Populate player inventory with hp-ico and mana-ico test items
- Fix TileView cell size to 128x128 and center tile positions
- Add virtual scrolling: only render visible rows in TileView
- Add mouseWheel override to TileView