Update min Dart constraint to 3.8, which will enable us to use the fancier collection literals. This requires bumping the min Flutter version as well: <img width="1892" height="1122" alt="image" src="https://github.com/user-attachments/assets/7c7b07fc-4d96-4987-824d-9a7133ecfb85" />
This PR adds the `WorldRoute` which acts as a normal route, but instead of adding a new component (page), it swaps out the world that the camera (either the default camera or an explicitly passed in one) is watching.
