Ray dashboards won't load due to symlinked files during install

**Describe the bug**

Trying to open the Ray dashboard in the NeMo-RL container will result in 404 errors and the dashboard will never load. This is due to Ray being installed in the `/opt/nemo_rl_venv` directory by `uv` but the main.js and main.css files used for the Ray dashboard get symlinked to `/root` as the container install does symlinks for all copies in the `uv` stages in the Dockerfile. The HTTP server used by Ray dashboard doesn't allow symlinks outside of the parent directory which causes the 404 errors. Instead, by using the `copy` link-mode during the `uv pip install` for Ray will fix the error.

**Steps/Code to reproduce bug**

1. Build the `nemo-rl` release container locally. Tested with commit `5514d1e6eb0036f4ccbc5dac42b1b860959d0087`.
2. Launch the container locally and expose port `8265` for the Ray dashboard.
3. Run `ray start --head --port=6379 --dashboard-host=0.0.0.0 --block --include-dashboard=true` inside the container to start the Ray cluster.
4. Open localhost:8265 in your browser to view the Ray dashboard - this will never load and there will be 404 errors in the browser debug tools.

Instead, this can be worked around by re-installing the `ray` package with `uv` and using `copy` link-mode. To do so:

1. Stop the Ray process in the container if still running.
2. Re-install ray with `uv pip install --link-mode=copy --force-reinstall "ray[default]==2.46.0"`.
3. Re-launch the Ray cluster with `ray start --head --port=6379 --dashboard-host=0.0.0.0 --block --include-dashboard=true`.
4. Open localhost:8265 in your browser - the dashboard should now load properly.

**Expected behavior**

Ray should be installed without symlinks so it can render the dashboard properly. As-is, the dashboard will not load due to the symlinks being in another parent directory.

The Dockerfile should be updated to either force-reinstall Ray without symlinks, or all dependences should be installed without symlinks, but that is less desirable.