core, frontends: fix invalid translatable strings. Some f-strings where used in translatable text, this has been fixed by using explicit `format()` call (using a script based on `tokenize`). As tokenize messes with spaces, a reformating tool (`black`) has been applied to some files afterwards.

version: "3.6"
services:

  backend:
    image: libervia/backend:dev
    build: backend-dev

  web:
    image: libervia/web:dev
    build: libervia-web-dev
    depends_on:
      - backend