refactor!: Item changes

- Bump version to 0.3.0
- Moved crate::inventory::item to crate::item
- Made Item.position non-option
- Renamed Item::new_positioned -> Item::new
- Removed old Item::new method
- Changed Inventory.can_fit signature to use item borrow

Cargo.toml

@@ -2,7 +2,7 @@ cargo-features = ["codegen-backend"]
 
 [package]
 name = "expedition_demo"
-version = "0.2.0"
+version = "0.3.0"
 edition = "2024"
 
 [dependencies]