Use local storage instead of cookies for settings

[zbynek]

Fixes #968 by not using cookies at all.

Testing done

Manually checked that changing settings and reloading the page preserves settings.
npm run test passes locally.

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• [n/a ] Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[timja]

@jan-molak possible to take a look please?

[timja]

or @basil maybe?