Merge ETH upstream changes into Edinburgh version

Major changes:

• Mantine LoadingOverlay being stuck to top left fix (was also fixed locally, prioritised upstream fix when merging)
  • https://gitlab.ethz.ch/vseth/sip-com-apps/community-solutions/-/merge_requests/411
• Editor now supports split-screen mode in addition to edit and preview modes, and has full-screen support
  • https://gitlab.ethz.ch/vseth/sip-com-apps/community-solutions/-/merge_requests/347
• Small visual improvements in the expert endorsement and vote count for answers
  • https://gitlab.ethz.ch/vseth/sip-com-apps/community-solutions/-/merge_requests/406

Commit log also references a migration from Create React App to Vite, which will likely be implemented in upstream in the coming weeks, but for now it was reverted due to a bug with LaTeX rendering (so no actual changes in the merge).