Migrate to Vite and add Docker-Compose healthcheck for database

Contains the following upstream changes from master:

• Migrate from Create React App to Vite (redo after a previously reverted merge)
  • https://gitlab.ethz.ch/vseth/sip-com-apps/community-solutions/-/merge_requests/410
  • https://gitlab.ethz.ch/vseth/sip-com-apps/community-solutions/-/merge_requests/407
• Add postgres healthchecks in Dockerfile to fix Django not finding DB locally
  • https://gitlab.ethz.ch/vseth/sip-com-apps/community-solutions/-/merge_requests/422
  • (Makes 20e508f8 redundant in our fork, but we'll keep it just in case)

Contains the following local fixes:

• Our fork has a custom link transformer for Markdown rendering to prefix any URLs beginning with a slash with the OG BetterInformatics domain; the migration to Vite (and react-markdown 9.0.0) breaks that, so e6226cea fixes it
• Upstream Vite config doesn't account for running the frontend in a container, 2e6b08a4 fixes it (will PR to upstream soon)
• During the merge, lockfile entries for local dependencies "tinycolor" and "jwt-decode" were lost, da177b16 fixes it
• Update CI to run tsc and eslint explicitly since we don't need to actually transpile and build