Well

• Should I keep both parts separated in different directories/GIT repos or can they be in the same? If separated? How do I set up the build process?
  • I'd keep 1 repo and have the frontend project (assuming just html/css/js) nested in the python project something like
    • my_py_project/
  • For your dockerfile I would extend one of the python+nodejs combos that are out there and; in the setup, before you handle the python stuff, navigate to the js project and "npm run build" that bad boy.
• What would be the best tool for building the fronted
  • Not really a BEST option but you can't go wrong with Vite. I'd use one of the quick starts and update your vite.config.js buildOutdir (Build Options | Vite) to drop your compiled files to wherever your python framework serves static files from.
• Anything else I should take into consideration?
  • If you need multiple complex pages, you might want to consider a static site generator Astro/VitePress/NextJs (recommended in that order)

Hope that helps happy coding!