Ensure HTTPS works

[wolframkriesing]

• [x] make HTTPS work (and HTTP locally for development)
  • [x] replace all KATAS_SERVICE_DOMAIN with KATAS_SERVICE_URL which contains the protocol too
  • [x] configure it properly for production
  • [x] make it work so in dev i can work with a local URL (on HTTP, to make dev simpler)
  • [x] housekeeping: use concurrently, to not have errors that parallelshell throws
  • [x] housekeeping: remove eslint, just adds noise in the code