Enhanced inventory grid and placement logic to improve item stacking, placement rules, and maintain item world size. Key changes include:
- Removed dynamic item scaling; items retain true world size.
- Updated depth lane ownership to prevent stacking conflicts and added placement validation.
- support duplicate stacking with new methods and optimized placement for cubic items.
- Adjusted rotation logic to clarify and fix footprint transformations.
- Updated grid offset and added safeguards for inventory toggling during object pickup.
Refactor inventory system for 3D grid-based placement
Improved modularity by separating grid management, item data,
and placement logic into distinct components. Added XML
documentation for better code clarity. Introduced metadata
for `InventoryGrid3D` to ensure proper Unity integration.
