Reduce vulnerabilities

I did not touch the code since long, so I need to update the libraries, at least to get rid of all critical vulnerabilities.

See output of npm install:

#UI
found 266 vulnerabilities (4 low, 72 moderate, 160 high, 30 critical)
  run `npm audit fix` to fix them, or `npm audit` for details
#Backend
found 215 vulnerabilities (1 low, 55 moderate, 141 high, 18 critical)
  run `npm audit fix` to fix them, or `npm audit` for details