WIP: Loot
- Physics: Added ContactReceiver interface and refactored Physics to support JPH::ContactListener. Scene now dispatches collision events to nodes via OnContactAdded.
- Scene Management: Restored scene.hpp by moving Scene and Physics declarations out of node.hpp. Updated includes across the project.
- Entities: Added Entropy node type with dynamic sphere physics and contact logging functionality.
- Assets: Integrated elements.blend and updated gameplay.json to include an initial Entropy instance.
- Gameplay: Adjusted player starting position in Gameplay::run.