feat(shell): run bash as a login shell to get hostname in prompt (#1336)

# Description

Running `bash -l` causes bash to source /etc/profile, which includes the
hostname in the shell prompt.
This is useful for keeping track of where retina-shell is running if you
have multiple terminals open.

## Related Issue

N/A 

## Checklist

- [x] I have read the [contributing
documentation](https://retina.sh/docs/contributing).
- [x] I signed and signed-off the commits (`git commit -S -s ...`). See
[this
documentation](https://docs.github.com/en/authentication/managing-commit-signature-verification/about-commit-signature-verification)
on signing commits.
- [x] I have correctly attributed the author(s) of the code.
- [x] I have tested the changes locally.
- [x] I have followed the project's style guidelines.
- [x] I have updated the documentation, if necessary.
- [x] I have added tests, if applicable.

## Screenshots (if applicable) or Testing Completed

<img width="530" alt="image"
src="https://github.com/user-attachments/assets/c16dc14d-a8b9-4e84-b19e-fb7e265b3a30"
/>

## Additional Notes

N/A

---

Please refer to the [CONTRIBUTING.md](../CONTRIBUTING.md) file for more
information on how to contribute to this project.

Signed-off-by: Will Daly <[email protected]>

shell/Dockerfile

@@ -25,4 +25,4 @@ RUN tdnf install -y \
 	wget \
 	&& tdnf clean all
 
-CMD ["/bin/bash"]
+CMD ["/bin/bash", "-l"]