Replace stale ctrl-next references left over from repo rename

[iamtanuj18]

Fixes #913.

The repo was renamed from ctrl-next to ctrl at some point, and stale references were left behind in three files. Docker prefixes volume names with the project directory name, so the actual volume is ctrl_ctrl-db (confirmed via docker volume ls), but the Makefile was still trying to remove ctrl-next_ctrl-db, which is why make clean failed with no such volume.

Per @plouka13's follow-up comment on the issue ("should look for any other stale content in ctrl around ctrl-next"), I did a broader sweep with ripgrep. Eight stale references across three files:

./README.md
7:  [![Build checks](https://github.com/Garvan-Data-Science-Platform/ctrl-next/actions/workflows/check.yml/badge.svg)](https://github.com/Garvan-Data-Science-Platform/ctrl-next/actions/workflows/check.yml)
85:Then from the root of the `ctrl-next` repository run the following commands:
216:Have a look through existing [issues](https://github.com/Garvan-Data-Science-Platform/ctrl-next/issues) for anything that you could help with. If you'd like to request a feature or report a bug, please create a GitHub Issue using one of the templates provided.
218:[See contribution guide →](https://github.com/Garvan-Data-Science-Platform/ctrl-next/blob/main/docs/CONTRIBUTING.md)

./docs/CONTRIBUTING.md
1:# Guidance for contributing to `ctrl-next`
3:- [Guidance for contributing to `ctrl-next`](#guidance-for-contributing-to-ctrl-next)
41:ctrl-next uses a recent Node.js version as specified in `.nvmrc` in combination with the yarn modern package manager through corepack.

./Makefile
53:	NODE_VERSION=$(NODE_VERSION) docker volume rm ctrl-next_ctrl-db

Replaced all ctrl-next with ctrl in place across those three files. After the fix, rg "ctrl-next" . returns no matches. Also verified make clean now runs end-to-end without the volume error.

[ignatiusm]

Thanks for this @iamtanuj18 . Looks good to me 🚀

Can you please also create an issue to do the same for the ctrl-docs site sometime? I suspect there may be traces of -next there too: https://github.com/search?q=repo%3AGarvan-Data-Science-Platform%2Fctrl-docs+ctrl-next&type=code

Nice work tidying up around the place!

[iamtanuj18]

Thanks for the review @ignatiusm! I've merged the PR to dev.

I've also created a follow-up issue on ctrl-docs to track the same cleanup there: Garvan-Data-Science-Platform/ctrl-docs#11